avgjoe

I recently purchased my 81 and the AC compressor was unplugged and the previous owner said he unplugged it because it was making noise. I wanted to convert to R134 so I took the compressor off and drained the oil and replaced it with the oil in the conversion kit. I replaced the seals, changed the fittings, drew a vacuum on the system, and charged it and all seemed well. I took it on a road trip and everything seemed to work fine. The next time I drove it I noticed a noise when the compressor cycled off and I discovered two things.

1. When the compressor cycles off the clutch does not disengage all the way and it drags creating the noise I heard. If I disconnect the compressor the clutch will disengage as it should. I'm not sure where to start. The clutch must still be getting some voltage that keeps it partially engaged?

2. I also discovered that the AC stays on all the time, even when I turn it off. When I turn it off the blower turns off but the compressor does not disengage. Any ideas?

I have not gotten a shop manual yet so I don't really understand exactly how the system works. I suspect I have two separate issues or could they be related? Any thoughts?

Joe

interpon

if off no voltage and clutch still on? verify..bad clutch..

also you should flush and change oil so all components have correct kind and amount of oil..

now 134 cheap enough to re-do..

did you change orifice screen? or check it?

if you did NOT replace compressor.. you can change clutch but i would consider replacing compressor after flush and oil change correctly.. you can get lifetime warrranty NAPA if you show proof of flush etc..and accumulator change (you should change accumulator a real PITA job)

avgjoe

I replaced the orifice but nothing else. I did the same on my 88 and it worked for the 12 years I had it so I'm hoping of the same results here. As far as the clutch goes when I unplug the compressor the clutch fully disengages so I don't think it is the clutch itself.

interpon

makes sense..if it was dry no mineral oil left...accumulator may get gummed up..
so the focus is voltage to clutch...

sounds silly but make sure the belt is tight and not slipping with clutch engaged...really tight and check condition of belt cogs etc

Yadkin

You can buy a new R4 compressor, orifice and accumulator at Rock Auto in a kit for just over two bills. It takes PAC 150 oil.

The accumulator is easy to get to once you take off the fake brake vent cover. It's held on with torx screws.

avgjoe

I actually just replaced the belt because it was noisy. It was old and glazed over. The new belt is nice and quiet but this did not change my issue. I haven't had time to dig in and do some more testing voltage and trace things yet. Hope to do it soon.

interpon

then triple check tension..the new one will stretch

Street Rat

The accumulator on my '81 was a bitch to get in and out. Just sayin'
Craig

avgjoe

So I had a little time to do some more checking and I got a FSM which is helping.

The first issue of the clutch not fully disengaging when the compressor cycles, via the pressure switch, seems to have righted itself after some use. When it cycles off, the voltage at the clutch goes to 0 and the clutch fully disengages as it should.

The second issue continues to be a problem which is that the compressor does not turn off with the switch inside. When I slide the inside switch to off, vent, or heat the voltage at the compressor clutch drops from 12V to 3.5V but it is enough to keep the clutch fully engaged. In short, I cannot turn off the AC compressor unless I unplug it. The fan does go to low speed as it should when I slide the switch to off.

I have attached a wiring diagram and there is a compressor control switch shown but I have no idea where it is located. Does anybody know? I'm guessing it may have a bad connection or be faulty? I suppose it could also be the selector switch?

Where is this switch located?

In this position I still have 3.5V going to the compressor clutch

interpon

Hmmm..
check wires for taps or hacks? Grounds?
switch itself inspection?
remove wire from compressor and check again for backfeeding somehow?

https://www.fluke.com/en-us/learn/bl...roubleshooting

Yadkin

The diagram on page 1B-3 looks like a relay (switch) is buried in the dash. But...

Look on page 8A-68 of that same manual that shows no switch (relay?). The wiring on my car matches up with this second diagram. This has the entire 3.2 amps of he clutch controlled by both switches and no relays.

I'm guessing that your dash slide switch needs to be disassembled and cleaned.

avgjoe

So I know it's been a minute since I posted about this issue but I finally got in there and disassembled and cleaned the dash slide switch and it seems to be fixed! Thank you for all your suggestions. It will be nice having this working correctly again.