You are a brave man, or one desperately seeking air conditioning. I have avoided the AutoTemp II unit on my car, so can't answer all of those questions, but regarding the AC pump:
There is a wire lead that goes to it on most cars that I have seen comes up along the passenger side of the intake manifold. Could be different on the 73, but check for the wire that goes into the AC unit. If it is disconnected or something silly, that could be it.
The pulley that is on the front of the AC unit spins around the crankshaft of a miniature 2-cylinder compressor in a freewheeling motion when the unit is inactive and the car engine is on. Applying current to the connection where the wire goes in activates the clutch mechanism, which allows the spinning pulley to grab and spin the crankshaft, and the thing starts working.
I have seen many AC units that have failed. They are miniature V-twin engines with pistons and rings and they need oil to operate. It is possible to have them sieze. I have had 4 cars where they had seized and if you physically grabbed the end of the clutch (car engine off, please), that you could rotate the AC crankshaft around a 300 degree rotation before the con-rod, now seperated from the siezed piston would lodge somewhere that prevented further rotation. Verify that your AC unit is actually a viable pump and not a defunct assembly of parts if you have not done so already.
You said that it ran before, so I'd be positive. Good thing might be to check the oil on that pump? There is a plug that you can remove to do this (See the service manual). I check the oil first when I get a car and try hard to avoid pushing the AC selector before doing so, as the one time that I did the pump siezed on the freeway and burned up the belts before I figured out that the horrible smell of burnt belt was in fact coming from my gorgeous car as I crossed the SF Bay Bridge with fellow motorists making faces and gestures at me.
I finally had some time to apply some of the suggestions from my previous post on this subject, my thanks Dave Duricy for his response to my previous post, and I pulled apart my Autotemp II servo unit, mostly to see if I could figure out how it is supposed to work, and now I have some further questions.
First off, I checked the master and fan switches on the heater box on the car. I found that the fan switch was bad and wouldn't hold vacuum, so it wouldn't turn on. The master switch seemed to be ok. Anyways, I jumpered both switches with short pieces of wire, so now they are permanently "on" and I have a functional fan.
Just today I took apart the servo unit, and found that there was signs of fluid in the part of the casing where the big motor thing is, the other three quarters of the casing were clean. After starting the car, I watched the servo as the car warmed up, to see if I could see any signs of it functioning. I didn't hear any noises, and when I pulled the case apart again, with the engine still running and at operating temperature, I noticed that the motor on the bottom of the unit would turn very slowly, and only if I helped it. The system appeared to be stuck on high heat, no amount of changing the temperature knob would change the temp, nor would changing from low to high a/c or how or high defrost, and there was no sign of the A/C compressor clutch working. I also noticed a slight amount of coolant inside the casing, again in the part where the motor goes,
although I could not see where it was coming in, and it remained only a small amount on the bottom of the housing.
My questions are, how do I test this motor in the servo to see if is in fact, actually working, and are replacement motors available and at a reasonable cost. Also I couldn't figure out the purpose of the smaller motor mounted in the top part of the server, it never seemed to do anything while I played with the system, and I couldn't determine it's purpose. And finally, how do I know if the a/c compressor clutch is engaged, I am assuming the outer part of the pulley should be spinning with the pulley? This was not turning when I checked it, no matter what setting I put the a/c controls at, including off. I am assuming this means the clutch has failed, or the compressor is not getting a signal to engage the clutch? Strangely, I seem to remember the last time I played with the system, the outer part of the clutch was spinning.
Anyway, I am hoping I can get some answers or suggestions from the gurus here, otherwise I will have to spend actual money at an a/c specialist in town, although I don't want to spend money getting the refrigerant flushed and changed over until I know the system is functional. And I am not to keen on paying their hourly charge for them to troubleshoot things, although I am beginning to suspect that this system is beyond my ability to troubleshoot. I may be able to swap on a borrowed unit from another car, known to be functional, so I can at least determine, hopefully, if the a/c compressor is funtional.
Robert Weldon
72 Imperial 2 dr (for sale)
68 Newport conv.
75 Dodge Dart Sport (factory air, presently missing a/c compressor)
97 Plymouth Voyager Minivan
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