Imperial Home Page -> Repair -> Electrical System -> Fuses
Question from Kerry:
Help! Ive got a short in my '54. Haven't started it since April but I uncovered it today and drove it to church. On the way back I noticed a slight 'burning' smell but not enough to think it was from my car. Parked the car for several hours and when I went back out it the battery was totally DEAD! Charged the battery and it started right up and I assumed I had left something on. Then I noticed the dome light was coming on for a few minutes and then going off. Further investigation showed the headlights also cycle on and off with the dome and interior lights.
Have had my head under the dash for a few hours and don't see any shorts or burned wires. It's a pretty simple wiring scheme. There is a breaker on the back of the light switch. I tapped on it but no change, again, no burned wires are apparent.
I know that if I start taking wires off one at a time,I can identify the particular circuit and I guess that is the next step. Anyone got any ideas that might help me make this easier? BTW, this is a 6V system but I don't think that matters.
Reply from Rodger:
As you know, you have the cloth wraped wiring in your car. If and when you find a break, and then repair that break you create another as you handle the wiring. I had this problem with our '47 De Soto Custom. I went to Rhode Island Wiring for a new wiring harness.
Question from Anthony (1967):
When you step on the brakes ---dash lights and running lights and turn signal fender lights up! Has anyone experienced this sort of problem before! I am visiting my mechanic again tomorrow---he is thinking there is some sort of grounding problem some where! Initially, he thought it may be a faulty turn signal switch---however----when the car is off and you depress the brakes, that is when the dash and running lights illuminate.
This is a very common issue with an easy solution. There may be a shorted bulb or pigtail probably in the Stop/Tail combo cct. Replace the bulbs in the rear of the car for starters then if that doesn't work, test all pigtails for continuity/shorts.
Have you checked your fuses? I had a blown fuse on my 76 that caused the dome light to come on when I pressed the brake pedal. It caused me much confusion too, hehe!
This sound like a bad ground at the tail lights. I have chased these a couple of times in the past. If your brake lights are dim it's the ground. If they are bright it's Brad's short.
Reply from John:
The tail lights should be evenly bright when not stepping on the brake. If any are too bright, you may have the wrong bulbs in some of them.
I'd start by checking all fuses. I've had strange lighting situations with a blown fuse in a '63. I would also check for pinched wires to tail lights & any wires near the brake pedal. Have you recently replaced any bulbs? If yes, are you sure they are the correct type? Is the turn signal switch a generic replacement or Mopar & is it wired correctly?
I agree with Craig, sounds like a ground problem.
Question from Bruce (1967):
Starting today, something is intermittantly haywire with the electrical system. Without provocation, the "charge/discharge" meter jumps almost all the way to "charge"(right). When it does, the aftermarket AC blower increases it's rpms dramatically. I turn off the AC blower (which also disengages the compressor) and the "charge/discharge" meter jumps THE REST OF the way to "charge". I take the car out of gear, tap the gas, and the problem goes away. It also goes away by itself, if I want to let it just burn a while (smells like electric smoke). Once the meter goes back to normal, I turn the AC back on and all is well for an unpredictable amount of time. It happened about 3 or 4 times during my half hour drive home.
Sounds like a pooched voltage regulator or a loose battery connection. Always check the cheap and easy things first.
I could be all wet here, but I think if you have a short circuit in an accessory with a circuit breaker I think it will make the meter do that. When the circuit is closed, it creates a big current load, and then when the circuit breaker gets hot, it opens and puts everything back to normal until the circuit breaker cools off, closes, and the whole cycle happens again. Whenever there is a significant load, the voltage regulator will send more current, which is why I think the blower would speed up. It may also make the lights brighter.
It would have to be something that doesn't have a fuse, but rather a circuit breaker. In my cars the only things that can do that as far as I know would be the power windows or the power seat. Everything else has a fuse and once a fuse blows, it wouldn't let the circuit close again. The circuit breaker would make a click sound when it opens or closes.
There could also be some corroded ground connections, and/or poor connections at terminals, but I would say that it is most likely related to a problem with the accessories.
I had a problem with my '59 Imperial being drained every time I went to start it, but could remember a slight clicking noise coming from the rear left window area prior to this happening. When checked on a volt meter you could see it surging periodically, and it turned out to be an extremely sensitive power window switch in the drivers master control which had fallen slightly into the door and was being slightly depressed by the trim edge. Don't know if a Dodge had power windows, but by 1967 they most likely had it as an option.
Had the same problem in a brand x (actually a brand V). The field (rotor) in the alternator was shorted. I've not played with my Imperial's charging system lately so I'm not really up on whether the regulator is before or after the field but if its after, then a short in the field would make it charge full blast. Its easy to check with an Ohm meter and a manual.
Question from Roger (1982):
This is plea for anyone with past history of fuse no.6 blowing on '81-'83 Imperials. I haven't had time to look at the car yet, I only noticed this morning on the way to work that the illuminated entry was not working, when I put a new fuse (30 Amp) in it just blows straight away. Fuse 6 covers : stop, under panel & door courtesy, map/reading light, door key cylinder, trunk, ignition switch, under hood & vanity mirror lamps, electric mirror motors, ignition switch time delay relay, electronic chimes, electronic search tune memory, illuminated entry electronics, electronic cluster memory & security alarm, electronic cluster seat switch. So you see why I am asking for a bit of guidance as I could spend a long time stabbing in the dark.
I don't think there is any easy way to track these down. Search your memory for any of these functions that are physically located near where you have done work recently (maybe a wire is touching something it shouldn't). None?
OK, then, search your memory for any of these functions that are physically near things that move (door and hood hinges, for instance). None?
OK, then, unplug the harness which feeds down the left side of the car to see if the short clears (it's behind the kick panel on the left "A" pillar). No help?
OK, then, now you need to get serious:
This is how you get serious - - - - Get a device used by pro shops that track down this sort of thing. These things can sniff out current flowing, even at very low levels. One installs a transmitter in place of the fuse, which allows a low level signal to flow without damage, then sniffs the harness with this device - it will lead you to the short like a bloodhound. I've seen this device in operation, and it is fantastic! The unit I have seen is the Leitenberger KSD 01.
Unfortunately, it is rather expensive - about 215 Euros, as I recall. For information, go to the Leitenberger GMBH web site at http://www.atg.leitenberger.biz/lrprodkateng/p_701.htm
I just fixed the same problem on my '81, not that you have the same problem I had but mine was a short in the passenger side mirror. The wire harness had rubbed where it went thru the door.
Similar problem on my '79 Non-Imperial LeBaron Wagon...the wire that goes through the rubbed hose and seals from behind the kick panel to the driver's side door had an intermittent short.. break.. and was rubbing against metal. For mine it blew the light on the bottom of the door. Also, the plunger switch which attaches to the front of the driver's door post to activate interior lights and door ajar buzzer when the door is open got bent somehow and the plunger switch unwelded from the nut... would throw sparks...so I don't now which of these problems caused the fuse to blow, but.. both were driver's side door shorts. It's possible my M-body LeBaron has a completely different wiring, but... then again... maybe not.
Question from Joe:
When the multiplugs were disconnected from the faux foot-well I could put the fuse in without it blowing, but when I did put the fuse back in I could hear a faint hissing sound from the light switch area of the dash which is a bit worrying!
My '83 makes some sort of a hissing sound whenever the gauges are "on." Meaning, whenever you sit down so that the gauge faces come up. If you pick your behind off the seat the noise goes away. I thought (hoped) it might be normal. Is this the noise you mean?
Let's not get a panic started here. The power supply for the dash display is an electronic oscillator which makes noise whenever the dash gauges are showing data. You can hear the noise very strongly if you have the AM radio on, but those with very good ears can hear the power supply "hissing" even without the radio on, especially if the engine is not running. The reason it stops when your butt leaves the seat is that it thinks you have left the car, and shuts off the display. These computers are clever, but you can outsmart them if you try.
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