Imperial Homepage -> Repair -> Air Conditioning -> Compressor
Question from Bradley:
I don’t want to sound stupid in asking this question but I am not mechanically talented. I have read articles on the list server about “checking” the “oil” in the air conditioning compressor to keep it from locking up. I have a 1968 car if that is important in your answer. The A/C blows cold although I would like it to be colder. Is there some kind of oil that is required in addition to the refrigerant? I know refrigerant is installed under pressure. Is there separate “oil” that is added through a dip stick tube like a car’s motor would have? Does it matter based on the kind of refrigerant I have? I don’t want to damage my car but I asked a local car club member about it and he said there is no such thing for my car as separate “oil”. Thanks for any comments you might have to clarify my ignorance. Ignorance is not bliss!!!!
There is a thin oil that is added to the compressor to lubricate the internal moving parts. There is no "dipstick" per se. I believe the oil is added when the compressor is first made, and some folks never add any more, going on the theory that only a small amount is required and it doesn't really get "burned up" or used like motor oil. But I think more can be added if necessary when the freon is changed.
However, the oil has nothing to do with how cold your AC gets, as I understand it. It is just there to protect the compressor from wear. I could be wrong.
I am definitely not a refrigeration expert. I have listened to air conditioning specialists over the years. There is oil in the air conditioning system. I believe the oil becomes suspended in the freon as it travels through the system. A problem arises when the system develops a leak. As the freon escapes, the oil goes right along with it. Repairing the leak and replacing the freon without paying attention to the oil can result in the compressor seizing or (in the case of our old Imperials) throwing a rod.
The best professionals evacuate the system, and then re-charge it with the proper amount of everything, including the oil.
Some compressors are piston type and others are rotary style. They both need lubrication just like any other "motor". Contrary to what was said, one can buy "Refrigerate Oil" separately. These days I believe that the product is called "Ester" and may be specifically for systems charged with 134A.
There is indeed a separate oil for your AC compressor . It can be added either right into the compressor ( a small wire can act as a "dipstick") or the preferred method of injecting it right along with the freon through the low side service port. The system obviously would have to be completely discharged to add oil into the compressor itself. Oil in itself has nothing to do with the cooling of the system but is quite important for lubrication of the compressor. That is the main reason behind having a low pressure cut-out switch which shuts off the compressor when the freon charge runs low-no freon flowing, no oil-result possible compressor damage. Depending on whether the system is using R-12 or R134 determines the type of refrigerant oil needed. Unless you've had a major leak of freon and a subsequent loss of oil indicted by a wet oil spot around the affected area, oil is generally not needed as the system doesn't "use" oil as your engine can. Hope this helps explain a little better.
Question from Londo (1964):
Looking for a New Air conditioning compressor for a '64-'66 Imperial. Are the new ones still available????
The A/C compresser in my '64 looks like the same ones used thru the '70's. One of my neighbors picked one up from NAPA. His truck is a '73. Looks just like mine!
They are still available - in remanufactured form anyway.
Question from Brian (1966):
Does anyone have a a/c compressor complete with clutch? I turn the a/c on and the car either stalls or sparks fly out of the clutch!
Reply from David:
Same thing happened on my '66, turned out that one of the pistons failed and seized. Kragen auto parts had one for me, there pretty common, except for the clutch. I found one in a junk yard.
Question from Tom (1966):
I have heard conflicting reports on whether the v-twin compressors can handle the new refrigerants. If they can should I do a rebuild on the one I have or just slap it back in? It didn't appear to have any leaks when I took it out.
It has been my experience that your stock compressor will do fine with 134a. Those a/c systems were massively over designed to be able to run the dual air option in the hottest of weather. My ’73 would freeze you out of the car with 134a and dual air although if the car was really hot it took a while to start cooling good. I imagine with a single air system you would not have the “lag” time like I had with the dual system.
Usually the front shaft seal is what fails on the compressor with age. Since you already have yours off I would have it rebuilt or replace it with a rebuilt. If it was still on the car I would probably chance it, but since yours is off and if you factor in the cost of the dryer and refrigerant etc it would probably be a good investment to have the compressor rebuilt.
When the whole R-134a situation was on the horizon and the upgrading to it was being discussed, I consulted with a friend of mine (an ex-Chrysler parts man) that worked for an a/c parts manufacturer. He said that the Chrysler RV-2 compressor (and I suspect the earlier RV compressor it evolved from, plus the other compressors used by the main stream American manufacturers in the middle '60s or so) were plenty stout to handle the added pressures of the new refrigerant. No need to change them for some of the newer Sankyo or similar compressors.
I concur that most everybody's factory a/c system on the bigger passenger vehicles, from about '65 on, were designed with enough capacity to keep everything nice and frosty in the hottest southwestern USA weather. I recall that one maker designed their systems to handle a 110 degree F day in Phoenix, sitting idling in traffic.
Although the compressor designs did improve, the key to the added cooling capacity was the huge condensors (with more fin/inch than the earlier models) they were using. If you look at some of the later '50s condensors, they don't have nearly as many fins/inch and resultant heat exchanging capacity as the mid-'60s condensors did.
One thing that has been noted about R134a conversions is that there is sufficient air flow across the condensor at low speeds. If the pressures go higher than normal, just like the R-12 systems, cooling performance deteriorates until sufficient air flow is restored (by vehicle forward movement or an extra electric fan kicking on).
In about '73 time frame, Chrysler issued a service bulletin regarding a/c performance. In certain conditions, it was possible for the hot underhood air to "recycle" and go back through the condensor and radiator. When that happened, the head pressure went sky high and the a/c hoses had popped. The cure was to put thin, die cut rubber panels in front of the condensor (on the sides between the headlight supports and on the bottom between the grille and the lower condensor; there was already a "yoke seal" that sealed between the hood and the core support) such that only "normal" air could enter the grille area. They also added a "Thermostatic Ignition Control" valve via a new thermostat housing. When the engine got too hot at idle, it'd move the vacuum advance vacuum from ported (no vac advance at idle) to full manifold vacuum (so the engine rpm would increase and the added fan speed would help cool the motor and the condensor down some)! .
One other thing my friend noted was that all of the old oil needed to be removed from the system. It would react with the new R134a (and it's different oil), congeal, and find the lowest spot in the system to settle out. That usually was the bottom of the existing condensor, further reducing it's heat exchanging capacity. I knew then that modern chemistry would result in more universal and more tolerant oils, but I would suspect that the best thing to do would be to, as he suggested, flush the system via the recycling machine with liquid freon to get all of the old oil out, then refill everything with the appropriate freon and oil. I know others have reported good results without going that far, which is good.
Question from Tim (1967):
I'm in need of a new A/C compressor for my '67. Can anybody give me any recommendations? Are there choices of compressors, is one brand better than the others, or are they all pretty much the same?
My receiver/drier has been replaced fairly recently. Is there any reason to replace it again when the compressor is swapped? What about any other components? I'll be moving back to hot, hot Texas next year, so I want to make sure this is done right!
In case it matters, my Imp is a non-Auto-Temp-Control model. And I plan to use good, old fashioned FR-12 Freon. Bring it on, baby, I wanna see icicles hangin' from those vents!
Reply from Bob:
You might consider the newer, Rotary compressor used on the, for example, '81 thru '89 full sized cars; the bracket will also be needed. These will be much smoother than the piston type that it will replace. If you system has been opened, or has leaked the existing refrigerant, you must replace the Dryer too, they're cheap. You used the term FR-12 - this is the preferred replacement refrigerant for the original R-12. This is because the thermal and chemical properties are most like the original R-12, (much of which is now available, made in China, and it's quality must be questioned). Also, the newer Compressor lubricant is now uniformly applicable to all compressors, regardless of refrigerant, and is also available - called Estercool oil and is compatable with the PAG, Mineral, R-134, and other lubricants. If you choose R-134 A, you'll have the risk of an evaporator that is too small, high and low temperatures that are not acceptable, and characteristics that don't "Fit" those of the Expansion valve.
Question from Tom (1968):
My mechanic has finally restored some semblance of functionality to the air conditioning system on my '68 crown convert - says the compressor runs all the time, tho - is this condition normal?
Reply from Brad:
I believe that is normal. The compressor should run any time the controls are set to anything except VENT or OFF.
Question from Demetrios (1968):
My compressor clutch seems to be making a clicking noise with both AC on and off that I do not remember being there in the past. The clicking has a metallic sound to it. I can't be absolutely sure that the source is the compressor, but that's what it sounds like. I recently replaced the fan clutch, but I don't think that could be the source. Is this something to worry about? Any ideas/prior experiences with such an issue?
I had a compressor that had a broken con rod and the crank slapped against the con rod when the magnet was engaged.
Silent when disengaged.
It does seem that the noise would be from the compressor. I have had good results with using a mechanics stethoscope to isolate noises, or you can just remove the drive belts from other accessories and note if the noise goes away or not. I would suspect the release springs in the clutch, they are small and only need enough force to keep the clutch " free " when the coil is de-energized. I doubt that the power steer pump would be making a clicking noise, though the mounting tends to let a chuckling noise ( yes, chuckling is how I have heard it described! ) which once you hear it you definitely know what it is. Alternator noise tends to be bearing noise and would be the opposite side, and the idler bearing would be a similar noise.
Not sure how much help this is, its basically a matter of eliminate the things that are right to find the thing that's wrong.
If the noise is there with the AC off, the problem is not likely to be in the compressor/clutch assembly, since with the AC off, only the pulley and its bearing is moving, and with the AC on, the pulley and bearing is rotating as a unit with the compressor crankshaft, so there is no relative motion.
I suspect the problem is elsewhere, but to prove it, temporarily remove the belts from the AC compressor and see if the noise is still there. Or, since it is easier on your car, remove the fan belt and see if the noise goes away. If it does, you know where to look from here.
Follow-up question from Demetrios:
I might try the test you suggested, but I am fairly confident the "chuckling" noise is coming from the compressor area. Dick, are you sure it would be a good idea to run the engine without the water pump spinning? I am sure its OK for a few seconds if you start a cold engine, but how long is too long?
Reply from Dick:
It won't hurt the engine at all (if it is full of water) to run it for 2 or 3 minutes without the water pump turning. Early cars didn't even have water pumps, you know.
On your car, the 2 belts for the power steering and for the fan are completely separate from the AC/Alternator belts, so you can take them both off and run each accessory independently, excepting only that you must run the alternator and AC pulleys together.
Question from Joel (1972):
When I try to turn on the a/c in my '72 it start making a grinding noise and then the belts gets loose. Nothing blows either, so not sure if it is the blower motor. Also does the duct running under the dash from the driver-side make a difference? Where is the thermostat, since it does not have the top thermostat housing on top of the block?
Grinding noise probably means bad compressor, no cold air means that the freon is low or gone, screeching belts means that they are loose or need replacing (is this the same '72 with the starting problems?, if so the screeching alternator belt is the same as this A/C belt). Also, a bad compressor can make the belts screech, burn, and break.
No blower function usually means bad blower motor or bad switch. If equipped with Autotemp, could be that the system needs diagnosis. This system has many parts prone to failure from old age and or lack of maintenance.
If your thermostat is not installed, you probably don't have any heat either. With Autotemp I guess this could impact the blower function since under certain conditions the blower won't turn on until the engine reaches a sufficient temperature. With no thermostat this temperature may not be reached except under extreme driving.
My best guess here is that the ac clutch is going or has gone, hence the grinding noises and the belts getting loose. It may be the compressor, but I'm thinking if the compressor was gone then the thing would either seize or you'd have looseness and such all the time....either way thats the area to start searching.
If nothing blows....I'm presuming no air flow here thru the ducts....does the car have any of the ATC systems? I'm no expert on them but I think the FSM will lead you through that, as in some cases the fan may not blow at all unless
other parameters are met.
The thermostat should still be on top of the water pump housing....it probably has an angled housing to get the upper hose to clear the a/c compressor. Follow the upper hose from the radiator back towards the engine....at the engine end of the hose you should find the thermostat.
Be aware, the stat itself shouldnt have anything to do with having ac or not. IF the compressor turns, has enough freon onboard and can develop pressure, and the sytem is intact then you'll have to find out why the fan blower isn't working and go from there. It may end up being a case of isolate and identify the separate problems and then try and tie it together.
Question from Jack (1973):
I'm looking for some thoughts on this: I got the A/C on my '73 running successfully 3 weeks ago. Now, the compressor started making a bad noise, and the belts are dancing, etc. the belts are new, and the compressor does work, but when the noise started, I shut it off. It's the original compressor, and there has been no leakage from any of the hoses or fittings on the system.
Did you check the tightness of the clutch bolt?
Turn the ignition to the "on" position, but don't start the car. Turn on the A/C. This will engage the clutch and keep it from free-wheeling. Tighten the bolt in the center of the front of the clutch as tight as you can get it.
Turn off A/C and start the car. Engage A/C.
If the noise has not gone away, you may have an internal problem with your compressor - possibly with one of the pistons.
The system may have been overcharged, causing excessive pressure and an overload on the compressor/clutch parts. If you don't think that is likely (if you know, what is the high side and low side pressures in the system when it is running?), then you need to investigate the mechanical subsystems.
First, take the belts off the compressor and feel the clutch pulley - is it tight on the shaft, and does it spin freely? If so, then engage the clutch with the belts still off (turn on the AC), and manually turn the clutch in the clockwise direction, feeling for any clunking or abrupt change in restriction to the rotation. Turn it through a couple of turns - it should begin to give you some hydraulic drag as the pressure starts to build up, but there should be no "hard" spots in the turning. Using these tests, you can possibly figure out if your problem is in the compressor itself (big money) or merely in the clutch (small money) or merely in the attachment of the clutch to the compressor (no money).
If you can't find anything wrong at all, try adjusting the belts so that they are quite tight, and if the belts are not a matched set, take one of the belts off so you don't have flapping due to mismatched belts. See if it runs smoothly that way. If it does, get yourself a matched set of belts, or at least get two from the same batch (if you go to NAPA, ask them to give you two that were made side by side - you can tell by looking at the plastic labels on the belts - they line up where they were slit apart). With our Mopar dual belt drive units, the old matched pair belt sets were essential to avoid this sort of problem, but now they have quit selling matched sets, saying "our belts are all matched because our production processes are now perfect" - yeah, right!
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