Repair and Diagnosis of Problems with Your Imperial's Alternator


Imperial Home Page -> Repair -> Electrical System -> Charging System -> Alternator

General Definition from Jay

Chrysler was the first to install alternators in their cars. Only the Valiants got them in 1960 as standard equipment. In 1961 all Chrysler products had them. It took many years for GM to switch over, mainly because they had such a large inventory of Generators to use up first. The principle advantage of Alternators is that they don't rely on high rpm's to produce a charge. They change DC current to AC current. Therefore, they can charge a battery even while the engine is Idling. Air Conditioning is a huge drain on the electrical system. Thus Chrysler used Alternators on air conditioned cars to extend battery life.

Tip from Bob (1981-1983):

Just above the two brush pockets on the large alternator on the "81-83" Imperial is an Air Conditioning muffler-to-hose connection; this connection will eventually leak freon and also refrigerant oil onto the two brush pockets below which will drastically affect the alternator output. In reading these notes about the Voltage Regulators and battery conditions, I cannot help but say something, again, about this inherent problem. Run your fingers under the connection, if it's wet with oil, fix the hose and then check the operation of the voltage regulator and the battery. You could well find that the oily brushes have isolated the field windings of the alternator and in some cases, overheated the battery because of a high charging rate - buckled plates, bulging battery case and short life.  

Tip from Mike on upgrading your alternator:

Thought I would share this info with others on the list. The original alternator on my 67 imp was always inadequate at idle and low rpm's. Especially with the lights on and the defroster fan operating. Being a single field type it just can't put out the current at low rpm's. I put a digital volt meter in the car so I could see precisely what my electrical system was doing, at idle usually less than 12 volts, at cruise 14.6, which means under-powering my car and draining the battery at low rpm's, overcharging the battery at cruise. I decided to find a better alternator. I took a measurement of the case where it mounts at the bottom and pulley, went to an auto parts store and looked/compared to some newer MoPar alternators. I found a late 80's dodge truck alt. with a pulley that was the same ,but a hair smaller diameter, the mounting at the bottom was the same but required switching the mounting bushings with the original alternator (the overall alternator case is similar the 67 alt., but larger). This newer alt is a dual field which puts out at least twice as much current at idle (the slightly smaller pulley helps even more). And puts out 86 amps at speed. Because of the larger current capability I by-passed the amp gauge in the dash (for safety reasons, having all that current flow thru the dash is a design flaw in Mopars anyway) and used the digital volt meter under the dash to monitor the electrical system. At the same time I upgraded to the MoPar solid state voltage regulator also. Now from idle to cursing speed, with all the lights on, fan on blinkers, brake lights, radio on it never goes below 13 volts and at cruise never goes over 13.7 volts, WAY BETTER. It works so well, I am very happy with it.

Addition from Bill:

Everyone is concerned about the volts being put out by an alternator, but overlook something that is just as important - AMPS.

Putting an 86-amp alternator will not damage your car's wiring or the alternator gauge - so put it back on line. Regardless of amperage, the wiring was the same for all units at factory anyway, with differences being made for options, engines and equipment. And it does not put out 86 amps continuously. Only up to 86 amps, if needed.

The most important thing to remember when replacing an alternator is to make sure the one you are buying is not putting out fewer amps than the one you are replacing. If you do get an alternator putting out fewer amps, you will have dimming lights at idle and the like.

I once owned a 1974 Sebring, 318, with a 60-amp alternator, The bearings went and I had it replaced with another. Turned out it was a 34-amp unit for a slant six Valiant. Being winter, the car was being driven with heater fan and lights on, plus the radio. Within three hours the lights were dimming when driving at 40 mph. The next day I returned the alternator and that was when the difference was discovered. Putting in a 60-amp alternator returned the electrical system back to its normal operation. With heater, lights and radio on, there was a slight discharge at idle (normal) but with the lights off, no discharge.

Question from Bruce:

As long as I have the alternator out of the mighty '78 NYB, I thought I should clean it up. But it seems like a bad idea to get a bunch of degreaser and pressure washer near it. Any opinions about what to use to clean the thing?

Reply from Eric:

Radio Shack or some other electronics stores sell "electronics degreasers, cleaners and lubricants" in an aerosol can. The can comes with a brush to assist in dirt removal. It has been very helpful in cleaning relays, switches and bushings.

Question from Roger:

How do you tell if a car has bad alternator or voltage regulator?

Reply from Matt:

Some classic bad alternator symptoms are: dim headlights, slow wipers , slow blower motor.  The best indicator of a bad alternator is the gauge in the car (if functioning) it will show if you are charging or discharging.

Question from Rolland (Interchangeability):

I need help on alternator replacement. Can the alternator of the 60's (6 round diodes showing at the rear of the alternator and one field terminal) be replaced by the alternator of the 70's (6 push in diodes in a rectangular configuration with two field connections)? If so what do I do with the extra field terminal? Can this just be grounded and if so which one is grounded?

Reply from Elijah

I just purchased a rebuilt alternator for my '65 LeBaron through the local Napa store. They had to order it (of course!), but it arrived the next day. As always, there was a little wrinkle in the process: the first alternator they got had a pulley that would barely turn! They naturally ordered another, which arrived a day later. It has the correct original round housing and round diodes, with the single field connection. I also ordered the replacement solid state voltage regulator -- Napa part # VR1001. I haven't installed these items yet, but I expect to see an improvement in the system, especially the elimination of the common flickering lights.

Question from Elisabeth (1961):

I have just bought a '61 LeBaron and I wonder about the alternator. Is the cut-out relay inside the alternator or is there somewhere else? In that case where can I find it?

Reply from Hlynur:

The cut-out relay is not inside the alternator. It is on the left side behind the battery where the starter solenoid is. (black box)

Question from Thomas (1962):

This is the situation. I have a new regulator, all electrical connections in the engine compartment have been cleaned, the battery seems to be OK (it's one of those with the green "light" indicator) and the dash gauge has been checked out. Now, this is what happens with the gauge. If the car has sat for a while and the engine is started, the gauge reads all the way to charge and then settles back down after a while. When I use the turn signals the gauge flickers to the charge side in time with the turn signals. When I run the windows up or down the gauge jumps over to charge until I release the window button. Do I need a new alternator or a new battery or both? Is either one not putting out enough amperage?


From John:

This sounds pretty normal except the high charge when starting. This could be a current draw such as a light on somewhere while the car is parked. The window motors draw a a lot of current & the gauge moving way to charge is normal.

From Dick:

This situation comes up often on these cars. Your ammeter is behaving correctly, excepting only that it is reacting too strongly to the variations in charge rate that occur during normal operation. If you search the archives for the discussion on replacing ammeter shunts, you'll see what to do to correct this. Briefly, you connect about 1 foot of # 18 wire from one terminal to the other on the ammeter. 

On your broken return tab on the TS switch, you should check out the replacement kits offered by NAPA stores. They make one for the later cars with cornering lights, and possibly they have one for your car. They are a real bear to install, but they do work.

From Pete:

Your electrical system is behaving exactly as it should. No need to change any parts.

From Adam:

My '64 Crown was behaving the same way, most Mopars of our vintage did. The dancing alt gauge and flashing headlights drove me nuts. It's the mechanical voltage regulator. Then Dick Benjamin told me NAPA sells an electronic voltage regulator to replace the OEM mechanical one. It's a little pricey ($53 or so) and they had to order it. Boy what a difference. Gauge is pretty steady and almost no flashing of headlights. Well worth the expense to me.

From PEN:

The temperature gauge has a pair of breaker points which regulate all the other gauges. Take out the temp gauge and very gently file the points. The alternator gauge swinging wildly is another story, having to do with poor grounds, a bad regulator, an alternator with bad diodes, and wiring problems. The oil pressure gauge will work with a new sending unit, which is on the back of the engine behind the carburetor, but only after you have fixed the regulator in the temp gauge. You might also want to invest in a new temp gauge sender unit, which is located on the water pump housing. 

Question from Patrick (1964):

Seems my charging system is out of commission. My battery is way too low for any kind of starting however the lights seem to still work as well as the power windows, just a bit slower and dimmer. I replaced my alternator with another I have, same with the voltage regulator. All the related wires are solid and verified that they are OK.

I'm lost at this point, I put the other three batteries in other cars that I used on the Crown Coupe during the replacement process and they are holding a charge just fine, just not in my Imperial. Anyone have any ideas for me?


From Mike:

Maybe you have a drain on the battery. There could be something that is causing the battery to run down prematurely. Make sure all dome, trunk, etc lights extinguish, same with brake lights. Then check for possible shorts to ground. Remove the battery cables and put an ohm meter across them, making sure the key is off and all accessories are turned off. If it reads anything other than infinity (or a really really high number) then you have a (partial) short somewhere. If you have a current meter, you can just clamp it onto one of the battery cables with the battery still connected and see if current is being drawn at "rest".

From Chris:

Sounds like the voltage regulator is definitely out of comission. There are two relay type contacts in these regulators, and chances are one or both is sticking. Your best bet is to replace the thing with a solid state equivalent.

From Robin:

I just wonder if you have put a multimeter switched to dc volts across the posts of your battery while the car was running? It will tell you immediately if the alternator is charging or not. Should read between 14 and 14.5 volts DC while running if your battery is low.

From Steve:

Do you have a meter? If not go to Radio Shack and get one. You will need one on the future to track down electrical problems.

With the car running check the voltage on the battery. At a bumped up idle you should have between 13.5 and 14.5 (rough numbers) volts across the battery. If you have this voltage then the battery is charging. Anything below 12.6 is not going to charge the battery.

Another possibility is that something on the car is running the battery down. You can also use your (new?) meter to check for drains on the battery.

Question from Bill (1964):

When our '64 Imperial "was" running then died (rusty fuel tank), while trying to restart it the battery (new) ran down quickly and the headlights were dim. When we finally did get it (jump) started I put a voltmeter on the battery and got 12.8 volts. I then checked the voltage at the "Bat" terminal of the alternator, there I got 15+ volts. What am I missing here, it seems to me I should get the same reading. The alternator is putting out, but the battery is not getting it.


From Phil:

You have a big voltage drop or resistance somewhere, and while the cables are a natural place to check, I'd also check your ammeter gauge. They can still read, and yet, won't allow enough current through to charge the battery, when bad. A common problem with 60's Mopars, and a real bear to find, if you don't know about it. Also, anyplace that is dropping 3 or so volts, will probably be warm, check carefully with your hand at your connections, there may be some unseen corrosion at some point, that is causing resistance. Check the firewall connector too, good luck!

From Denis:

I just went through one of these problems with a car of mine, and after changing the battery, regulator, generator, cables, it turned out to be the starter, that for some reason was pulling amps of the scale of the gage used by the mechanic. The starter has been rebuilt and the car start and runs OK. For some reason if I turn a corner to sharp, or without the use of the accelerator, the car stops running and must be restarted. Carb stuff, I would guess?

From John:

Probably is carb related, but I'd start with a fresh fuel filter if its not new already. If the idle is extremly low, raising it a bit might help. Also check for any leaking vacuum hoses.

From Loren:

I see mention of electrical problems with a '64 Imperial and questions of where the power may be going, or, in my case, not able to go, and it brings to mind the last time my car rode home on a flat bed tow truck. My electrical problem was caused by a loose connection between one of the wiring studs pressed through the metal plate that holds the ammeter magnet and needle and the metal plate itself. There are two studs extending from the back of the gauge. The positive circuit that powers the car passes through the brass plate, in on one stud and out on the other. The magnet on the bottom of the ammeter needle just reacts to the changing magnetic field created by the power passing through. One of my splined posts had spun in the brass plate and was therefore not in direct contact at all times. The break in the circuit caused my car to die when coasting to a stop at a stop light. After wiggling wires, cleaning contacts and messing around for about an hour, it started again, once, and then never would start again. Hence the ride home on the flat bed tow truck. When the short was located, I repaired it by replacing the pressed in studs at the back of the ammeter with hex head bolts, star washers and nuts that locked the bolts against the brass ammeter plate. Before you spend a lot of money replacing major electrical components, check the ammeter gauge. If the studs move in relation to the brass plate this may also be the source of your problems. A clue to the problem would be deformation or melting plastic at the back or bottom of the ammeter gauge. This problem is not a loose wire connection to the ammeter studs but a faulty connection between the stud splines and brass plate. When I put my ammeter gauge back together, I found my headlights no longer get dim at idle like they have done since I first got the car.

Question from Johan (1965):

My alternator finally gave up (very little charge in the battery after a good long idle and a jump start, cranks a couple times though) and I'd like to replace it with more amps.

Should I get a stronger alternator like 65-amp (I've got air conditioning)?  If I do this, will I need to upgrade anything else like the volt regulator?  The lights, radio and wipers all dimmed or slowed down when idling. Could this just be the old alternator showing wear before the final breath?  The battery is brand new, belts were tight and the tires are Michelin....

Reply from Carl:

You're opening a can of worms, trust me on that!

You can get a stronger alternator, what I am currently looking at is the Leece Neville alternator found in many SemiTrucks out there, the reason is that it'll charge damn near fully at idle, it'll give you 100 amps and it has externally replaceable brushes!

To some that may be overkill, but I have plans.. hjeh hjeh hjeh

Anyway, what you should do FIRST (assuming you're not SURE your alternator is dead) is to make sure your battery-ground is good, take the connectors off, sand the area and retighten the cable, also check the ground at the bulkhead connector and also the little cable from the block to chassis between the firewall and block on the passenger side.

If your alternator is bad, the best bet is to get an UNrebuilt one from a junkyard or parts car, that way you get better charging than if you buy the rebuilt parts shop ones, they usually have mismatched parts. On the other hand, you may just pick up a 100amp (or 80amp as many 80's Mopars had) one at the store, that should do you good.

Oh, alternators are deemed good if they give you a charge at 2000rpm, mine is struggling with the high beams, heater on full, brake lights, turn signal and windshield wipers. That's what I need to fix!

Follow-up from Johan:

Will I have to get anything upgraded as well like the volt regulator?  I'll probably be going up to around 40 or 50 amps.

Reply from Carl:

You shouldn't have to swap anything else as the current is just a formula for the voltage and resistance. What you'd need is to upgrade your wiring, especially ground wires. The older and crustier the connections and wires are the higher the resistance is, the higher the amps get and the hotter the wires get, bad case would be hot enough to start a fire!

Question from Rob (1966):

I have a charging problem with my '66 Crown and am hoping someone can offer advice. My alternator gauge was flickering periodically from 'charge' (normal) to 0 and finally went off the scale to the charging end. I reasoned the problem was the voltage regulator and replaced it. Now the gage flickers constantly. Instead of a periodic symptom I now have a constant one. Any ideas? I did check all the connections and all seem good.


From Elijah:

I was having a similar problem with my '71 Imperial. I replaced the voltage regulator, with no result. The next thing I did was to replace the alternator (which turned out to be good, since the bearing was going bad in the old one). This didn't fix the problem either. The solution that I found was to go to Radio Shack, buy an aerosol can of electrical contact cleaner, and clean all connections at the alternator, voltage regulator, and also at the bulkhead disconnect on the firewall. I also used needle-nosed pliers to *carefully* tighten all the connectors. Somewhere along the way, I cleaned or tightened the right one, and solved the problem

From Bill:

This sounds more like a short circuit to me. By chance did you put the old regulator back on to see what difference it made? You may have got a bad new one or the wrong one. I don't have my FSM with me. Join the chat, I'm going there now. Maybe we can figure it out.

From Michael:

I had similar problems with my 68. It sat for several years, then put into service without replacing the alternator. The gauge began to "flicker" and I assumed the voltage regulator.  Replaced it with no change. It finally began to fluctuate wildly or discharge steadily. I replaced the alternator and solved the problem. A similar situation can be caused by a bad ground at the VR. I use a MOPAR electronic, and if the ground is not great it will cause the same symptoms. I have not seen the same with a mechanical regulator.

Question from Mark (1966):

I have a problem with my electrical system.  I just replaced a dead alternator (bench tested zero output) in my '66 Crown Coupe. After the new alternator was installed, the electrical system fluctuates. The faster the rpm's, the faster the pulse. The lights are nice and bright, except at idle.  Do I have to replace my voltage regulator? Was it fried when the alt. went bad?  Am I barking up the wrong tree? Any thoughts out there about this? 

Reply from Dick:

I don't know how much your needle is jumping around at idle, but some of this is quite normal if you have the original type mechanical voltage regulator. It is not a continuous control device, it is an on-off device. It has to sense the battery voltage and decide whether or not to supply some charging current, and it does this many times per minute. Each time the battery voltage increases above the design norm, the regulator will stop the charging, waiting and checking until the voltage lowers slightly from the drains on it caused by the engine and accessories that are operating. When little or no current drain is occurring, the voltage drops very slowly with the regulator in the non-charge state, then when it reaches the threshold, it clicks back on (and it is a relay, not a smooth adjustment). This is what happens several times per minute when the car is idling. 

When you have a heavy drain on the battery, the regulator senses this and keeps the alternator supplying a charging current continuously, so you don't see the flickering of the needle. 

When you rev up the engine with little or no load on the electrical system, the charging rate available from the alternator is so enormously over what the battery needs periodically that the "on" time for the regulator is a very small fraction of a second, and so the ammeter gauge does not have time to react to this momentary pulse from the alternator, thus you do not notice the cycling at higher RPM's. 

If all of this gets on your nerves, you can change over to a modern electronic voltage regulator, which performs exactly the same function but does it smoothly, so you don't see the needle twitching at idle. You can also install a shunt across the ammeter terminals, this will reduce it's sensitivity, and damp the movements somewhat. I recommend about 12 inches of #18 wire for a shunt. This will get somewhat warm, so don't coil it up in a lump or tape it to other wires, just loop it gently behind the dash.

Question from Gary (1966):

I have a '66 Crown and from time to time the alternator gauge goes right to the right, then after a few minutes comes down.  Someone told me that they make an electronic voltage regulator.  Can someone shed any lights on this?


From Dick:

It is normal for the gauge to indicate a heavy charging current for a short while after a heavy drain, such as from starting the engine, or leaving the headlights on for a while with the engine not running. This does not indicate anything wrong. 

If you mean the gauge goes completely to the right extremity of the gauge, a likely possibility is that your shunt is burned out, or not making good contact. If this is the problem, you should also see an extreme discharge indication (deflection to the left) when you turn on your lights with the engine off. 

If you do, you need to take the gauge unit out of the dash and install a length of wire from post to post on the ammeter terminals. About 1 foot of 14 gauge wire will bring the gauge back to normal operation. This wire will get somewhat warm, so let it loop by itself, don't bind it into a bundle of other wires. It is very important that this wire be connected very securely, so use a soldering iron to install ring lugs, and make sure everything is clean. 

If you only see this extreme indication in the charge direction, there may indeed be something wrong with your voltage regulator, but if that is the problem, you gauge will not be going all the way to the peg, as the alternator can't put out that much current regardless of what your regulator is telling it to do. Are you experiencing rapid loss of battery water? (This would indicate chronic overcharging.)

From John:

The first electronic regulator for an Imperial that I know of is on the 69.  It does sound though that you are getting the early symptoms of regulator failure. Before changing though, you may want to make sure that all connections are tight at the regulator & also at the alternator.  Also, listen closely to alternator with engine running for bearing noises.  The alternator could be beginning to fail.  Both regulator & alternator should be available at your local parts store if needed..

From Ben:

I just installed the solid state regulator in my 64' Crown and my flickering lights and wild ammeter problems were solved!  There are available from NAPA.

Question from Ken (1967):

I need some help again. The alternator in our 67 Imperial w/AC went out and needs replaced (bearings froze up). The alternator has only one wire going to it for a hook up. Exactly what size alternator do I need. I've read from 55 amps to 75amps. I'm confused and need you advice.

Reply from Roy:

It's a 60 Amp alternator. They are plentiful and cheap, but usually need to be ordered from the local warehouse, so expect to wait a day or two. I think I paid $30 with a $5 core and it was at the store the next day.

Question from Tim (1967):

When I start my car, the alternator gauge is fine. Right smack dab in the middle. Put the car in gear, and the little red light comes on and the gauge drops a bit. Once I'm moving, the light goes out, until I turn on a blinker or something. Then the light imitates the current draw.  The idle of the car is set very high in case that has something to do with it.  I've taken the belts in hand and they are tight. (They do need replacing.)   I don't have one of those electrical current checkers. Are they easy to use/understand?  Is there something other than the alternator I should be looking at to solve this problem? (The battery is brand new.)


From Scotty:

Well first things first : Check the cables for corrosion and looseness check where the output lug is for corrosion and looseness most of the time that happened to me it has been a bad voltage regulator a cheap and easy part to fix . go down to the local auto parts store and get an inexpensive volt/ohm meter and check out put at the alternator it should be around 13 to 14.5 volts if not check the connection from the volt regulator to the alternator clean it and then recheck voltage if still low take the alternator off and go to the local parts place like PEPBOYS, NAPA, or some such.. they will test the alt for free and if checks cool get a voltage regulator ..if this doesn't solve it then you have a serious problem like a partial short to ground when the engine is in gear ..then its a process of rooting around the electricals until you find it.

From Richard:

The best check for alternator/regulator problems is any voltmeter you have laying around, or can get hold of. Put it across the battery and measure the voltage without the engine running. After starting the engine the voltage should increase slightly to about 12.5vdc. Next turn on the headlights, if the charging system is working, the voltage should jump to about 14.5 vdc. Without a meter and in the dark: Set the engine idle to the correct speed and turn on the headlights. If the lights are sort of dim while idling in gear, and get brighter as you increase engine speed (slightly): bad alternator. When you replace the alternator, replace the regulator. Trust me. While your under the hood, check this: on the right side wheel house is a 10 or 12 pin connector for the engine wiring harness, which includes the field leads for the alternator. The contacts are generally green w/ corrosion. Check the bulkhead disconnects (firewall, below power booster) while your at it. In fact, check all the connectors under the hood for corrosion and/or loose/frayed connections. I'm sure you'll find several. Cracked battery terminals wouldn't be a surprise either. One last thing, the 100 amp alternator uses rubber insulating boots in the mounting bolts and has an external ground wire (housing should not be grounded). The insulators crumble over time, and the ground wire often breaks.

From Bill:

I have had similar problems in the past and it has been either a wiring short or problem or voltage regulator. Not real familiar with a 75 but I think the voltage regulator is built into the alternator. If you have a volt meter you could check the output. The easiest way is to go to a service station that can check your whole charging system with their equipment. Most will do this for free or very nominal cost.

From Frank:

Well, lets first start with some background. The gauge set in the 75-78 Imperial / NYB consists of gauges for temp, charge/discharge, and fuel. Within each gauge is a LED. The LED for temp and fuel is slaved to the gauge, so that when high temperature or low fuel is reached the LED confirms the reading. The LED within the alternator gauge is a bit different. It does not indicate discharging, but rather low battery voltage. I just double checked the factory manual, and unfortunately, it only says that the LED illuminates when the voltage falls below "a pre-determined point." I would estimate somewhere around 11.5V. 

OK, so what you have is probably low system voltage and some charging, since you don't mention the need to jump-start the car, or charge the battery frequently. Thus, the problem you most likely have is either: 1) Worn field brushes that are not transferring enough current to the alternator field to sufficiently charge the battery 2) Some shorted or open rectifiers inside of the alternator. 

I'm betting on #2 since the ammeter does not indicate discharge consistently. I'll also bet that you are hearing quite a bit of alternator whine in your car's stereo system. I always knew it was time for new rectifiers when the battery seemed weak, the ammeter stayed kind of centered, and there was a bit more noise in the stereo! 

What to do? Your car probably uses the 100 amp alternator. This unit has 12 rectifiers arranged in 2 sets of 6. One set for positive and one for negative. You could go out and buy a rebuilt alternator. But if the bearing in your alternator are still good, you can just replace the rectifiers. Why? It is MUCH CHEAPER to replace the rectifiers than to get a rebuilt alternator. A few months ago, the alternator got weak in my car. (This one is not a Chrysler product, but an alternator is an alternator.) Poked around with a DVM and found that the regulator was regulating, but the alternator was not putting out much current. Pulled the alternator and put it on a solid bench and spun the pulley. The armature spun easily and quietly, so the bearing were OK. Called around and found rebuilts at the dealer for $170ish; auto parts had them for $130ish. Called a starter generator rebuilder and bought the rectifiers for $25! (Most auto parts can order them, too.) Figured I'd splurge and bought brushes for $4. So, if I were you, I'd fix what I have and pocket the $100.

This really is a simple service job and is darn hard to goof up. I've actually done it in under an hour WITHOUT getting dirty. (Of course my car is still pretty clean under the hood since it only 7 years old and has just 143K miles.) 

Remove the battery ground cable. 

Pull the alternator and remove the wires. 

Remove the brushes (white plastic carrier on the back of the unit. It is where the two field (blue and green) wires attach.) The case should be stamped "FLD" 

Remove the screws that hold the two halves together. 

Separate the two shells. There is a slot to insert a screwdriver and pry a bit to get the process started. 

Keep the stator with the back side of the alternator. (The stator is a ring that looks like a stack of metal rings with heavy wiring running through it.) 

The wiring of the stator is connected to the rectifiers. There are three nuts that hold the wires to terminals on the rectifiers. 

Remove the nuts that hold the stator wiring.

Lift the entire stator free. Don't pull or bend the wires unnecessarily! Everything should just lift off and the wire should just slide up off the rectifier terminals. 

Using a VOM, or a DVM (CAUTION, ONLY USE A DVM THAT HAS A DIODE TEST POSITION!) check the rectifiers. Current should pass in only one direction. The negative rectifiers are near the periphery of the case. 

The positive ones are near the center. If you get continuity in both directions, you have a shorted rectifier and must replace that set. If you get no continuity in either direction, you have an open rectifier and must replace that set. 

Remove the screws for the bad set and replace. Reassemble the alternator in reverse order of disassembly. Oh, when reinstalling the brushes, the long terminal one goes on the bottom and the short terminal goes on the top. (Assuming that you have the alternator positioned with the pulley down.)

From Dick:

The red light is warning you that your alternator is not putting out the normal full charge. It is working, but not up to snuff. The red light should not come on at idle, especially if your idle is set high.  

Take your alternator to your local el-cheapo auto parts place and get a rebuilt (make sure you get the right amperage, it will be in your shop manual-electrical specifications section, and is probably a 63 AMP unit). Most of the ones on the shelf will be 45 AMP units, which will work in a pinch, but your car needs the extra capacity because of all the electrical gee-gaws on it, especially in the winter. 

Your existing alternator probably has two burned out rectifier diodes, and one still working, giving it a maximum output of either 15 or 21 AMPs, depending on which size it is. You cannot tell by looking at the size of the case, but if you look very carefully you will see the capacity stamped into the rear housing of the alternator on the outer circular surface. It is usually something like "45A" or "63A" or the like. 

I'm not sure which of the many electrical testing devised you are referring to, but I would advise that you get a VOM and a High current magnetic coupled type of current meter for your tool box. You will use them all the time, and no, they are not difficult to understand. 

The high current meter is useful for checking starter draw (usually on the 400 AMP) scale, and alternator output (usually on the 50 AMP scale), and is used by merely holding it in close proximity to the wire through which the current is flowing. Instructions for positioning the meter and avoiding interfering metal objects will come with the meter, or if they do not, I can help you with that. 

The VOM is used for a multitude of tests, it will measure DC and AC voltages from a few hundredths of a volt to 1000 volts. It will measure resistance from 1 OHM to Mega-OHMS, and it will measure current from tenths of amperes to 10 AMPs. They are available from Radio Shack for under $50, and will save you one hundred times that much in not having to depend on the local repair guy to figure out what is going on with your car's electrical system. It will come with very complete instructions. 

You need to understand only this: 

1. Voltage ("E"), Current ("I"), and resistance ("R") are related by this simple equation...........E=IR. 

2. Power ("W") can be computed by taking W=EI. 

3. Your battery stores power (never mind how) in the form of available current at 12 volts. 

4. Your battery stores energy in the form of power (12 X AMPS) times the length of time for which it can deliver such power. Thus the rating on batteries used to be in "ampere-hours" and a typical rating for a car like yours would be 75 AH. Unfortunately, lately battery vendors have begun hiding the AH rating in their catalogs, and selling batteries by CCA ratings, which is cold cranking amps. These are also important, but make identifying the largest capacity battery for a price difficult to identify, you have to look in the electrical spec. to find it. Your owner's manual tells you what was standard in your car when it was new. Often in lesser cars, larger capacity batteries are an option, but an Imperial would automatically have the largest capacity battery (of the required physical size) available 

You can play around with this information in various ways. For instance, if you have a 75 AH battery that is completely discharged, and an alternator that is putting out 63 A, it will recharge the battery in about 1 1/2 hours, plus some additional time to account for inefficiencies like heating effects, but say 2 hours to be sure. If your alternator is only capable of 15 A, and you run your starter at say 300A to start the car for say 10 seconds, once the car starts, it will take the alternator 200 to 300 seconds (5 minutes) to bring the battery back to the state of charge it was in before you started the engine. And if you drive off with your lights on, which take about 15 A on bright, leaving nothing for the battery, you will never bring the battery back to full charge. That's why you need a big alternator on an Imperial.

Question from Mac (1968):

I have put both a new alternator and a solid state voltage regulator in my 68 Imp. For some reason it still is not charging like it should.  If I am driving with the lights and heater on it is the meter shows a slight discharge. When I go to stop, and the lights and heater are on, the meter almost maxes out on discharge. But when driving during the day the meter shows a charge, but only to the first increment on the meter.  Dick said to check the meter and make sure it is centering properly.  I did, with nothing on and at and idle the needle sets dead smack in the center. I am going to get the alternator tested again today.  Maybe they sold me a bum alternator.  Also, the previous owner put new ends on the battery cable instead of replacing them, could that be a problem as well.


From Dick:

If your car cranks at a normal rpm, the starter must be getting adequate current, so your cable ends, while ugly, are not the cause of this problem. It sounds to me that your alternator is either a smaller rating than required (which I think should be 63 AMP for your car, check your FSM) or one or more of its diodes are bad. I do not think it can be your meter calibration, since it shows normal discharge when the lights are on and the engine is off etc. I doubt it is the voltage regulator, since in that case the battery voltage would be too low after a few days of driving like that, and I assume it is charging to 13.5 - 14 volts or so with no electrical equipment on and the engine idling. (You might want to verify that, but I bet it's OK.) 

Testing of the alternator is definitely the right move. Be sure to verify that the belts are tight enough. They don't need to be very tight, since you have a dual pulley, but they should feel pretty snug. If that were the problem (loose belts), you would likely hear some screeching when you first turn on you headlights.

From Bill:

When I recently needed a new alternator I asked the guy at NAPA if there was a more powerful version available, there is, a 60 amp as opposed to a standard 36 amp. The old one on the Mopar in question was working but was making some noise under heavy load and I replaced it as insurance as I was leaving on a long trip, but the new 60 amp seemed to make a difference at idle speed compared to the old one.

Question from Bob (1969):

My question deals with my 1969 Imperial.  I took my Imperial for its first spring drive today. Everything seemed fine for the first couple of miles and then I heard a clicking sound. It sounds like it is coming from under the dash in the left corner. I also noticed the alternator gauge going to discharge every time the clicking would start. Any idea what I should look for?


From Steve:

Sounds like something is stuck on and overloading the circuit until the circuit breaker trips and then the situation repeats when the breaker resets. Some things to check would be windows, seat, and headlights. On my '59 one window switch sticks in the down position so even though it looks like it is off it continues to energize the motor.

You need to find this problem before the device in question cooks itself from the overload.

From Elijah:

Your problem may be with the headlight door motor. Try turning the lights on for a moment, and then turning them back off. Or open the hood and find the knob on the bottom of the headlight door motor -- give it a couple of turns and see if this helps.

From John:

Coming from that area, it would most likely be a stuck window switch or a seat motor switch.Try all of the window switches as well as the seat switch & be sure they all function properly.

Question from Elijah (1971):

For a couple of days now, when I start my Imperial, the alternator whistles. This noise usually lasts for about 15 or 20 minutes, then disappears. So what's the deal? Bearings going bad in the alternator? Do I need a new one?


From Dick:

If you're sure the noise originates in the alternator, my guess is, "yes" and "yes", respectively. If you're not sure, use the vacuum cleaner hose trick to listen to it. (Take a vacuum cleaner hose and hold one end to your ear, the other to the suspected noise source (keep your fingers out of rotating parts!) and you can localize the source of a noise within an inch or so.) A broomstick will do the same thing, but it is somewhat hazardous, being rather unyielding if inserted through the fan blades while pressing on ones eardrum. If the noise seems to be originating in the front pulley area, try a brief squirt of WD-40 on the belts, just to eliminate the possibility of it being belt noise. I have heard really weird belt noises, they can masquerade as just about anything.  

The bearings in an alternator are cheap and easy to change, but you do need to know what you are doing. If you are not experienced, it is probably best for you to pull it off and take it to a rebuilder, or to your local "El cheapo" auto parts shop and exchange it. 

There is one other possible source of noise in an alternator, the brushes singing on the slip rings.  Either way, you need to get a professional to take care of it for you.

From Roger:

Water pumps do the same thing when they get old. Could also be power steering pump, but I never had one go on me.

From Bob:

My alternator failed last year on a return trip from Las Vegas. After stopping for a while, there was a howl like a banshee from under the hood - it was the belt trying to turn an alternator that did not want to rotate. A rebuilt replacement was $28.

From Paul:

Sounds like the front bearing. Not too hard to replace if you have the puller to remove the pulley. Rebuilt units are available probably for under $50. I have usually decided to just replace the alternator rather than the time to replace the bearing. If you have little Alternator/generator/starter type specialty shop nearby, you might check out their prices on rebuilding or repairing your unit.

From Ron:

Chances are, yes. The noise you hear sounds like an almost dry bearing, which after running awhile warms up enough to spread the last remaining lubricant around. There are rebuild kits available, however with the low cost of rebuilds and lifetime warranties, it is hardly worth it. When it makes sense, I always rebuild my own as I am retired and have the time to do so.

Question from Frank (1971):

I am hoping someone can point me in the right direction with this. The car is our '71 New Yorker.  Here are the problems:  

1. The lights get dim and often get brighter as the rpm of the engine goes up. Does this mean a bad voltage regulator?
2. My wife was driving the car a few months ago when the lights went out on her. She says they were completely out for the whole trip home. The next day the car was able to turn over and start then stalled. After a jump the car started fine and gave us no problems for over two months. The lights have always stayed on since. I thought maybe the switch was getting bad and tried moving it around in different positions to find a bad spot but I could not get it to fail.

3. The battery is a sealed type with the built in hydrometer.  I noticed the window is clear with no "green eye". I guess I can assume the  battery is bad. I had to jump the car for a second time last week when it got cold here; the battery has held a charge since.

I was thinking maybe a bad voltage regulator could have cooked the battery and causes the lights to get dim and bright.  Does this sound right?  Can the lights going out completely for one time be part of the problem or is this a separate problem?  To complicate matters I  have also noticed a noise which I think could be coming from the alternator.   Should I just buy a new regulator and change the battery or is there something else I should be looking at?

Reply from Dick:

Sounds like you have a plethora of perplexing problems! 

1. The light intensity varying with engine RPM is normal, to some extent, more noticeable especially if your battery has begun to fail  (sulfate), as it's internal resistance is going up and it takes a much higher charging voltage when the engine is revved than an healthy battery would. So step one is to investigate the battery, or if you want to go the easy way, just go to your local friendly Costco Store and plop down your $50 or so for a new store brand battery, the highest CCA rating you can afford and will fit in your battery holder.

2. The "lights going totally out" needs some more info to diagnose. We need to know, did the headlights go out but the dash and running lights stay on? If so, the problem is likely one of the following devices, in order of  likelihood: a. The dimmer switch (assuming here that you do not have "Twilight  Sentinel".  If this assumption is wrong, let us know and we'll  rethink this and the following:  If it is the dimmer switch, try wiggling the connector to the switch contacts, and also operate it a few times to see if you can catch it blacking out the lights momentarily while it switches.  This is a common failure point and symptom on all cars; these are cheap and easy to change. b. The headlight switch. If the headlight switch is beginning to act up, you may be able to tease it into a state where the running lights come on but the main headlights do not. If this is easy to do and can occur without special fiddling with the switch, it's time to replace it. c. The headlight circuit breaker. This is not a normal failure mode for the circuit breaker (that's why I place it in the least likely category) but it is possible that the circuit breaker tripped and did not automatically reset in a few seconds so as to make the headlight blink on and off every few seconds as it is supposed to, but rather caused the headlights to totally quit until much later. I'd suspect this failure mode only if all the others are eliminated.  On the other hand, if "lights going totally out" means all the lights, dash and marker, tail and front parking lights ALL went out, this is really strange, but since they later worked OK, one has to suspect the headlight switch or the operation thereof. 

3. It sounds as if the battery has died. Assuming it is at least 3 years old, I would simply replace it. There is no reason to suspect there is anything wrong with your voltage regulator, it has done exactly what it is supposed to do. 

4. Don't spend money on a new alternator without knowing it is the source of the noise. Step one is to get a short length of garden hose and use it as a sound probe, one end at your ear, the other waving around under the hood until you locate the source of the noise. If it appears to be at the front of the alternator, get a can of WD-40 and spray a tiny amount on the alternator belts as the engine idles. If the noise immediately goes away (probably for just a few seconds), your problem is belt noise. If it bothers you, replace the belts after you thoroughly clean all the pulleys.   If it doesn't bother you, slam the hood and drive off with the radio playing, it won't hurt anything to make a little noise up there.   If the noise appears to be coming from the back of the alternator, or does not quit with the WD-40 trick, visit your friendly local auto parts place and pick up a rebuilt alternator, unless you like to rebuild them yourself. They are easy and the parts are cheap, but this does take some skill and experience. Usually all that is needed is the bearings, and some alternators seem to wear out their slip ring contacts (read: brushes) but that usually takes at least 100,000 MI.

Question from Elijah (1971):

This weekend, I pulled the instrument cluster out of my '71 Imperial LeBaron, and replaced several items, including a broken odometer and trip meter, as well as a couple of non-functioning gauges. After I put it all back together, everything is working fine.  EXCEPT -- now, when I start the car, the alternator gauge swings wildly to the right (charge). And, when I drive, any small change in the electrical system, such as a turn signal, causes the alternator gauge to fluctuate quite a lot. Also, if I turn the lights on, the gauge shows a charge as long as I'm moving, but if I stop, it swings far to the discharge side.


From Dick:

Do you have a shop manual for the car? If so, look at the ammeter connections on the instrument schematic and see if the gauge is supposed to have an external shunt ( a wire connected from one terminal on the gauge to the other one). If the shunt is external, you must have knocked it off or broken the wire. If it is internal, it won't show on your diagram, and you will have to replace the gauge unit. The purpose of the shunt is to conduct the majority of the current around the gauge without running it through the gauge. If the shunt is not connected, the gauge will be hypersensitive.

Follow-up from Dick:

After I signed off last night, I took the '72 manual and did a little more study. The shunt is contained in the main harness on the engine side of the firewall, and consists of a spliced connection between the red #10 wire and black #10 wire that come through the firewall on pins 16 and 25 of the main bulkhead disconnect. In 1972, this was called splice #3. See if you can identify it from this. If you can, unwrap it and inspect for poor connection, you may have to strip it all apart, clean everything, and resolder the splice. An alternate procedure, and probably easier for you, is to install a replacement shunt right on the ammeter terminals. It is a bit of a hipshot as to the size, but I would try a 12 inch length of #16 wire (stranded copper, of course, and solder the terminals on the ends of the wire, do not trust crimp on terminals for this) for a start, then see if the gauge is back to acting normal. If it is still too twitchy, shorten the wire. If it is really insensitive, lengthen the wire. This wire is going to get slightly warm, so do not bundle it all up in a ball and tape it, just let it wander around by itself in the open air. Do not ignore this problem, because it is affecting the alternator charging rate, and making everything electrical in the car overly sensitive to engine RPM.

From Frank:

I am pretty darn certain that your car, as my '72 did, uses an external shunt. The bad news is that I seem to remember that the shunt was in the wiring harness somewhere. I don't remember if there is overload protection in this circuit, but remember that the alternator's full output current is about 65 amps. If the engine is not running and you are drawing current, that also runs through the ammeter. (Figure about 20A for headlights, 15A for interior lights, and you start to get big numbers. You don't want to run this amount of current through the ammeter, something will eventually voice its displeasure. I had a '73 shop manual somewhere and I just can't put my fingers on it right now. I'll need to look over at Dad's house. Try to go back over what you did when working on the dash, to see if that provides any clues. Also, did the meter work before?

From Dave:

First, make sure that your instrument cluster is grounded properly...automotive electrical systems do really wild things if ALL of the separate ground wires aren't in- stalled where they belong. Also make sure that both wires are snuggled up on the back of the ammeter, loose connections here will cause these problems and others. 

Second, remove the voltage regulator from its place on the inner fender and clean the spot where it is mounted, as well as the screws and the base of the regulator it- self. The regulator must be well grounded too. 

Third, make sure that all wiring attached to the alternator is tight and corrosion- free. Be careful if you decide to remove and clean these, since the large red wire with the ring terminal is the alternator output and is connected directly to the positive side of the battery...remove the ground terminal from the battery to prevent fireworks in the event that you accidentally ground any terminals while you are cleaning them. 

Fourth, loosen the belt on the alternator and try to move the shaft from side to side. You shouldn't be able to! If you can, then the bearings have gone bad in the alternator itself and will have to be replaced. This will also cause the symptoms that you are describing.

From Mike:

I've always seen this happen on my '64 and '66. In fact, when my '64 came to me, the ammeter was burned out, and there was an after-market one stuck under the dash (and completely out of sight while driving). I got a replacement from Lowell Howe. My '66 looked like it might be the same, but it 'freed up', and turned out to be fine. I seem to remember seeing this on other Mopars of the era, too.

From Ken:

Make sure it's not the belt.

Follow-up from Elijah:

I have solved my fluctuating lights problem.  In essence, after I disconnected and reconnected the connections in the engine compartment at the bulkhead disconnect, the alternator gauge has returned to normal. Whew!

Question from Mark:

The gauge for the alternator, which has "D" on one side (for "direct") and "C" on the other (for "current") is acting up. Usually, the needle stays right around the center of the gauge. But now it goes over toward the right, toward "C," and hovers about around the 3/4 mark . . . while I'm pressing the gas. When I let off the gas, it drops back down toward the middle. Anybody know what's going on?


From Rob:

It may be that your alternator is failing, and only puts out enough amperes when the engine is revving at higher RPMs (indicating charging a taxed battery). This had been going on with mine, and when my battery finally died and I bought a new one, the garage did a quick test on my alternator and it was almost kaput itself. Replaced it with one out of an outfit in California that puts out 65 amps (rather than the original 35 output). Works great. So, best guess, test your alternator, and then get one that puts out more juice.

From Dale:

The "D" means discharge and the "C" means charge on the gauge. There must be a draw on your battery and when you run the motor at faster speed the alternator is charging the battery. I had a voltage regulator stick on my '67 Fury once causing the system to charge continuously... the darn thing started an electrical fire because the wires overheated. Look for a drain on the battery. Seems to be the most logical thing.

From Leo:

I believe the gauge indicates "discharge" and "charge" with the middle being status quo. As the RPMs increase the alternator is sending more of a charge to the electrical system hence the needle pointing more towards "c". There may be a problem developing with the voltage regulator developing.

From Joe:

My gauge always points a little over to C when accelerating, especially when running the a/c and lights, or after the car has been sitting a while and the battery needs a little juicing. Running steadily, the needle should be in the middle, even with sundry accessories going. If it's pointing to D, the alternator is not putting out enough juice- like when the idle is set VERY low and the a/c and lights are on. Basically, your alternator and the gauge are working fine, re-juicing a battery that sat for a while.

From Randall:

Possibly the belt is slipping or it could be something very simple like the battery water is low. I always look for the simple stuff first but your voltage regulator is working overtime (assuming the meter is accurate).

From Bill:

It sounds like you have two problems. A blown fuse and a faulty alternator. The fuse would control both instrument lights and the tail lights. The discharge would be voltage regulator and/or alternator. You need to check your charging system to identify what caused it. Improper voltage would blow the fuse and also take out the alternator. Don't put on a new alternator before diagnosing the problem or you may ruin it.

From Chris:

First, consider what this gauge indicates: the relative amount of current being developed by your alternator to run the car's electrical components and re-charge the battery to restore the energy you used cranking that big 440. That said, if you're not running any strong consumers (headlamps, for example) and the gauge stays toward the C for a while, you run the risk of overcharging your battery, which could cause the acid inside to boil or explode. Not a Good Thing! However, if you car sits for extended periods, or if your battery is getting old, it might take the alternator a little longer to re-charge the battery, especially if you had to crank the car a long time to start it. Here's what I'd check, assuming the ammeter is staying well towards C for more than a few minutes of driving: 

1. Make sure your battery connections are clean, tight (Don't over tighten them: Remove them, clean them and reattach them snugly.) and made with good cables. If you've never replaced your battery cables, now might be a good time. 

2. Make sure your battery has sufficient water, if it's not the sealed type. If it's sealed, check the "eye" for chargeability. Maybe it's just time to retire the battery... or it's a defective one. 

3. Check the condition of your alternator belt. There should no more than 1" of play (press down with your thumb midway between the two furthest-apart pulleys), and the belt should feel pliable and rubbery on the two sides that form the "vee." 

4. Get your charging system load-tested. It's not that expensive or difficult (even Sears or someplace like that could probably handle it without damaging your car!), and it'll let you know if your alternator is producing enough current (not just voltage) at idle and under load, and if your regulator is controlling the voltage properly (most importantly limiting it). The other issue is the apparent rev-dependency of your charging situation. Since the alternator puts out more current with more rpm, this apparent over- charging seems to me to point to a glazed belt (that slips at low rpm) or a defective voltage regulator. 

A related question from Mike:

My 66 crown is giving me the same trouble. It has sat for a while so I'm sure the battery is low, but when I was trying to start it I noticed a small burning incense type smoke coming from a little black box on the driver-side wheel well and the writing on it was illegible. Are the two related?

Reply from Bob:

Little black box is your voltage regulator. You can get those at pretty much any parts store, and they cost about $20. Takes more time to write about it than it takes to remove and replace.

Question from Justin (1972):

I have a '72 Imperial  and I want to replace the factory alternator with a higher power one, I am looking at about 100 ampere or more. Has anyone out there put a larger one in, or have one???  My alternator is only kicking out 50 amperes.


From Carmine:

I've did this swap to my 77NYB. I added a heated back-glass from a '78, which requires a 100 AMP alt. I had the entire '78 NYB as a parts car. The only wiring differences I found was a heavier gauge wire. Instead of a complete swap, I simply added an extra, heavier gauge wire in tandem with the original. You might have additional difficulty since the 100 AMP alt didn't exist in '72.

From Bruno:

I did find a 100 amp unit at a Mopar swap meet. Probably came off of a police cruiser. It takes a different bracket, but the same regulator. It is about 30% larger.

From Bill:

Don't forget to change your regulator when you do this switch.

From Joe:

If you want to install a higher output alternator, I would suggest that you invest in a suitable shunt and a separate ammeter to handle the higher current. The ammeters in MOPAR instrument clusters do not handle higher current very well. Usually there is significant heat build-up and corrosion from the heat and sometimes the result is melted plastic in the instrument cluster. Also if the current to the existing ammeter in the dash goes through a firewall connector, this is a source of overheating and melting of plastic materials as well. High output alternators should be routed direct to an ammeter (without going through any intervening connectors) and then to the rest of the circuitry in the car. 

For the most part, Chrysler had ammeters that were more than adequate for the accessory loads they came equipped with. Unless you have gone to high output halogen headlights and added a lot of accessories to your car, you probably don't need a higher output alternator.

From Matthew:

Just as added info, I believe that the first year Chrysler offered the 100 amp alternator was 75,due to the added demands that the Rear defrost (grid type new for 75)put on the electrical system. You'll note that the different bracket also positions the alternator higher up so that its at almost the same level as the A/C compressor.  I don't know if the earlier 69-73 Imperials have enough room for this swap, you may have to get your 65 amp converted.

From Bob:

The 100 amp alt is larger than the regular alt. and is a different shape, squareish instead of round. All the 100 amp alts I have seen also used a large one piece stamped bracket instead of the two arms that the regular alt used. 

From Jack:

Summit Racing sells a 105 amp alternator upgrade kit for $36. Fits 61-71 Chrysler alternators.

Question from Nils (1973):

What is the correct current-output for an alternator in a 73 Imperial? Seems mine has died, at least the battery is not beeing charged anymore.

Reply from Pete:

I don't have a '73 spec. book but I do have a '71. I'm willing to bet that the '71 and '73 are the same.

According to the book, a 71 Imperial without A/C had a 37A alternator standard. '71 Imperials with any type of A/C had a 60A alternator.

BTW, if your car has the original alternator, it should have a circular anodized aluminum tag under one of the case screws. That tag will indicate the alternator part number and current rating.

Question from Tim (1975):

I've removed the alternator from my '75, I took it apart, and now I'm lost.  Are the rectifiers the three little things connected to the housing by all the screws?  I can't just lift it out as Frank suggested, so therein lies the confusion. The stator came right out with no problem. In fact it was really easy to get this far!  Now where are the brushes exactly? The is no white plastic carrier attached to the alternator. I did find the places marked "FLD". ( I cleaned the whole alternator in a pail of gasoline to get all the gunk off. It did a great job of cutting the oil and grease)  I also cannot for the life of me find how many amps my alternator is. It  isn't marked on the case anywhere. Any ideas? (I've ordered a shop manual, but it's 7-10 days) On a similar note, the little cap on the end of a wire (the red one with the white stripe that goes to the alternator to one of the "FLD" terminals) came off. How do I reattach it?


From Dick:

My advice considering the situation is to put it back together so that it does not look like it has been disassembled (they won't take it as a core otherwise) and take it to your local el-cheapo auto parts place and swap it for a rebuilt. They can look up the correct rating in their catalog, as long as they look up the right car, you will be OK. Be sure to compare the mounting holes and pulleys to make sure it will bolt right on. As for the wire whose end came off, if you don't have a soldering iron, buy a crimp-on terminal that will fit and squash it on to a clean stripped end of the wire with a regular pair of pliers (assuming you don't have a crimping tool). Be sure to tug on the wire to make sure it won't pull out on you. If you do have access to a soldering iron, this will make a better repair, but the difference is not too important on the field wire. If it were the main alternator output, I would strongly recommend soldering the terminal onto the wire, since it conducts a lot of current, but the field wire is basically a signal wire, not a high current connection. In any case, all that matters is that the electrical connection be made, what kind of terminal or "cap" doesn't matter, unless you are going to have the car judged.

From Bob:

I endorse Dick's advise. When my alternator on my '66 seized on a trip 2 years ago, I was able to replace it far from home, but outside a friend's business late on a Saturday night. He took to the local Kragen's parts (I think) and we had a rebuilt alternator for $28 in less than 5 minutes. Installation was about 30 minutes. I don't know if the rating is correct, but it's kept the old Sear's battery charged for these two years. You can now use the time and money saved to work on something else!

Question (1981-1983):

When driving from Minneapolis to Tulsa, the voltage light illuminated on my 1982 FS. After rebuilding the alternator, the problem went away. Until last week.  After about twenty minutes of driving, the light came on (on  2 consecutive short trips). It got a new voltage regulator last year.  What is wrong now? Could the diode in the instrument panel be bad? I  have a spare alternator I may install for troubleshooting. Any ideas?

Reply from Frank:

The light illuminates when system voltage (measured by the dash computer) falls below 11.2 volts. First, check voltage at the battery with the engine running. Run at 1250 RPM. Voltage should be as below: 

Temp near regulator       Voltage range 

-20F                                14.9 - 15.9 

80F                                 13.9 - 14.6

140F                               13.3 - 13.9 

above 140F                     less than 13.60

My 83 Imperial, charges at about 13.4 when the engine compartment was hot. 

If voltage is low: ALL CHECKS are IGNITION ON and ENGINE NOT RUNNING, unless otherwise noted. 

1) Check regulator has a good ground. (grounded by mounting screws.) 

2) Check that there is full battery voltage available between ground and the DARK BLUE wire from the regulator's connector.

3) Check that there is battery voltage at the DARK BLUE wire on the alternator.

4) With the engine running check the voltage @ the battery while QUICKLY connecting the DARK GREEN wire from the regulator's connector. 

5) Check that there is near zero resistance from the battery's POSITIVE connector to the output stud on the alternator. 


1) Bad regulator ground. Clean ground connection around mounting screws and re-test. 

2) Lower voltage at regulator than at battery. Check for faulty wiring. 

3) Lower (or no) voltage at alternator blue wire - wiring fault 

4) Voltage does not rise to 14+ volts, alternator / wiring fault. Connect DARK GREEN ALTERNATOR wire briefly to ground. If voltage at the battery does not rise to 14+ volts, alternator failure. If it does charge, wiring fault. 

5) Resistance in this wire is a wiring fault. 

If the voltage is not low at the battery, check the wiring to the dash cluster. Ignition voltage is on pin 3 (Dark Blue wire). Battery voltage is on pin 1 (Pink wire). Ground is on pin 2 (Black w/ Light Green tracer). Check voltages and ground.

Question from Tony:

Today, my alternator seized up. As luck would have it a U.S. parts supplier in the North of England has a replacement at a reasonable price which I would like to buy. Although it is listed as a '61 Imperial unit, it is the heavy duty 60 amp version. Can these be fitted without affecting the voltage regulator or the battery gauge?  I remember about 25 years ago having a problem with another car which had a non-standard alternator fitted.

Reply from Mark:

I did that once and never had any trouble.  I can't remember if the ammeter was affected--I just told my mechanic up front that he should install an alternate gauge.  I assume this was more accurate.  It still operated fine when I scrapped it 150K later...when there was more rust than car.

Question from Frank: 

I have been working on my nervous ammeter problem and I am not sure what the next step should be. So far I have: replaced the regulator with a solid state unit. Cleaned all the connections on the alternator, both ends of the neg. battery cable and the connections on the cable between the engine and the body. With the engine off the gauge is at the center line. With the engine off and lights on the needle drops between the center and left hand line. With the engine on and the lights on the needle swings between the left line and halfway between the center line and the right line. If I rev the engine with the lights on then the needle will swing faster between the left line and all the way to the right line. I also noticed a chirping noise that coincides with the flickering lights and the swing of the gauge. I think the noise is from the alternator but the gauge was jumping before the alternator noise started. Any thoughts on this? does this sound like the shunt or a ground problem?


From John:

This sounds like the alternator is failing.  It was told to me many years ago that it is often wise to replace the alternator & the regulator at the same time, that if one goes bad it was an effect the other.  You may also want to check the wiring where it connects to the ammeter.  I had (2) '63s  that had the wiring insulation melt at this point, allowing the wires to touch.  

From Mikey:

Not being able to see the car from here, it appears that the basic function is correct, as far as the position of the needle at various charge and discharge positions.  The swing as you so accurately call it, is the needle reacting to the current flow to and from as it passes through the ammeter.  A shunt, is simply a parallel circuit and a ground in this circuit would most likely be seen as a dead short.  If you go back through the index, you will find a very satisfactory solution is found by installing a piece of 16 or 18 gauge wire between the 2 posts on the back of the ammeter.  This shunts some of the current, bypassing it from going through the ammeter, so the swing is less pronounced, yet the operation is unaffected.  A bonus is that this lessens the heat that is sometimes generated at the ammeter posts, which can cause the posts to melt the plastic insulating washers.  The noise you hear, the chirping, could be the belt momentarily chirping or one of the bearings.  I have heard this on all 3 of my Mopar products of this era.  It is possible that a diode is gone or going, and when it does the current momentarily increases and the pull against the belt changes.  A very practical solution, and actually rather easy, is to at sometime install the later model isolated field type alternator and solid state regulator.  We have this on 2 of our older Mopars and the charging rates are rock solid and the flicker and ammeter swings are much, much less, in fact - nearly impossible to detect!

From PEN:

I hesitate to try to answer this because I still don't have the final answer, but perhaps some people may get onto the right track. I started to have the flickering lights problem nearly 20 years ago with my '62: the bouncing needle of the ammeter. I went through voltage regulators from aftermarket sources, and most would stop it for awhile, but then it would start up again. The best success I had was when I put in an original Chrysler voltage regulator. That stopped the problem for about three years, but then it started up again. I think the problem is not only deteriorating ground connections, but also deteriorating positive links in the charging system which cause electrical resistance and thus voltage fluctuations which confound the system. The really sad thing is that the flickering lights seem to have an impact on the alternator. The alternator contains, I think, five diodes which create direct current out of alternating current. This situation seems to put a lot of strain on them, and the alternator can be ruined or much reduced in capacity as this problem continues. Definitely check the electrical connections going through the fire wall, consider running a separate ground wire from the alternator to the voltage regulator, check all grounds, try a solid state voltage regulator -- those are now readily available.

Question from Rob (1983):

Does anybody know if my '83 would likely have a 100 amp alternator? I assumed they'd all be the same, since there were no options, but the NAPA site indicates at least 2 alternators. I have to disconnect my a/c and leave the compressor off because it interferes with my new intake. I figured I could get the belt from a Cordoba/Mirada with no a/c, since my belt will no longer be going around the a/c pulley. Problem is that the NAPA site indicates different part numbers for 100 amp and non-100 amp alternators. Worse, it indicates that the belt is the same for a 100 amp with or without a/c! That can't be right. The belt would have to be considerably shorter.


From Dick:

I can't say for sure, but I'm about 95% certain it would have a 100 Amp Alternator (unless there was a larger one available, which I doubt). The '81s used a 100 Amp alternator.

From Dick:

100 A has dual belt and an external fan.

From Dave:

All 81-83 Imperials came with a 100amp alternator as standard equipment. As for the belt length take a piece of string and run it around the pulleys, then measure the length. This is not an exact science but it will give you a place to start. By the way what intake manifold did you use? I used an Edelbrock Performer on my 360 and everything bolted right up.

From Dennis:

Actually only the '81 Imps came with the 100 amp. alt. Although they look identical,the '82 and '83 Imps have 114amps of power. All the Imperial alternators have dual belts and external fans. The difference is internal.

From Dan:

'80's Imps have 100 Amp alternators with dual belts.

Question from David:

Does anyone have any advice to offer on finding an electrical short in a car?   My  Imperial has a short of some kind that kills the battery over a period of a few days when the car sits in the garage. I don't recall ever having tackled such a problem in the past. Where does one began, the fuse box perhaps?? I know there must be a general set of methods/steps for finding electrical problems. 

Reply from Mark:

Does this car have an alternator?  What you describe here is sounds to me like a classic case of an alternator with a diode shorted inside. It may not show up as low charge on the ammeter (amp gauge, charge light, whatever), so I would take the alternator to a local car parts store and have it tested.

Question and Tips from Ed (1981-1983):

I've been rather quiet on the IML lately, but my intermittent no-start problems have continued with my 82 EFI. As you may recall, I changed the Fuel Pressure Switch to a higher-pressure unit, and that seemed to help, but the intermittent no-starts continued. I initially thought that the no-starts were only when the motor was hot, but I found that they also occurred when cold. In addition, I have had the car suddenly stall-out, sometimes while driving at speed, for no apparent reason.

This seems to me to indicate a problem with that darned (not the word I usually use, but I'm TRYING to be polite!) Auto-Shutdown Module. Now, I did install an extra ground wire to it some time ago, as has been often-suggested by Dick B., Bob H., and others. I ran the ground wire from the ASDM mounting screw to the alternator grounding point, although I did not install an insulation barrier between the ASDM and the fender. When I have had no-start problems, I found that if I removed the ASDM wiring harness and bypassed it by jumping the two larger wires, the car would start right up. 

So now I have decided to leave the ASDM bypassed for testing. I made a jumper wire that fits into the harness connectors and used electrical tape over everything to keep out dirt and moisture. So far, I have not had a single no-start or stall with the ASDM bypassed. I'd love to find a new one, but I refuse to send that crook Brad's NOS any more money. Does anyone know of another source for these units? I just assume leave the stupid thing disconnected--the only hazard I can imagine is in the event of an accident, where the motor has stopped and the key is still on, as the control pump would continue to pump fuel into a non-running engine and present a fire hazard. I do have an additional used unit that I obtained from a local acquaintance and co-81-83-Imperial owner, but I have no idea if it is any more reliable than the one on my car now.

Reply from Dick:

While these modules have a bad reputation, when properly grounded they are usually trouble free. I'm convinced from what you have done to troubleshoot this car that you very likely have a bad one, but rest assured most of them are not bad, so since you have a spare, (and after building up confidence in your problem diagnosis by running it bypassed), you should be able to safely substitute the other ASDM and go off into the sunset.

I am not sure I have an exchange unit ready to go here at the moment, but if the replacement unit does the trick for you, send me the suspect one and I'll see if I can troubleshoot it for you. My guess is that there is a cracked "plated through hole" on the circuit board, and inserting a piece of wire and then resoldering all connections will probably return it to reliable service. The biggest pain in the posterior is getting all that goop off the board so I can work on it! 

The circuit itself is really quite simple - I've commented before that the designer must have been fresh out of engineering school, as he made some really amateurish mistakes in circuit design which make it especially susceptible to transients. 

Perhaps a later version has some filtering on the input/output leads to help this, Bob Harris would know if there is an improved unit in circulation. I do feel it is best to isolate the unit from the inner fender electrically, so that any funny business that occurs involving other electrical signals on the inner fender will not upset the ASDM's tender feelings.

Question from Allen:

I tested my alternator and it is making 18 volts and sending all of this to the battery. I put a tester on it tonight. It appears that the alternator has one field terminal and a battery terminal, but that somewhere in the splicing, the alternator regulator is not regulating or is being bypassed.  Is there a way to check the voltage/alternator regulator out to see if it is faulty? 


From Dick:

Pull the field wire off the terminal on the alternator. 

If A: The alternator quits charging, it is functioning normally, and the problem must be with either:  1. The field wire, most likely it is mis-wired to some source of battery or ignition voltage rather than the correct terminal of the regulator, or 2. The regulator is putting out a call for max charging voltage regardless of actual need. This would be because of a bad ground at the mounting of the voltage regulator or a failed regulator.  

OR-----  B: The alternator continues to put out too much voltage even with the field

 wire disconnected. This has to be an internal problem with the alternator, throw it back at the rebuilder for credit and get another one. If you are unable to do this, we may be able to troubleshoot it, but you are going to have to disassemble and reassemble it, and this is not easy or simple to do the first time. Don't take it apart without further instruction.  I'm going to switch this thread back to the whole IML, because there may be some who will also need to sort this out someday.  (Just to bring the rest of you up to date, Allen has been fighting an overcharging situation with his car, evidenced by boiling battery juices, extra bright lights and a smell of rotten tomatoes under the hood).

From John:

Another possibility is that the ballast resistor has been bypassed.  Also, is the correct electronic voltage regulator in place?

This page last updated August 24, 2004.  Send us your feedback, and come join the Imperial Mailing List - Online Car Club