Good afternoon,

The AC compressor in my 1980 C3 randomly started making noise, before I hit the internet and start throwing money at the problem, I'd like to hear the thoughts of forum members that have a better understanding of the AC systems these cars come with. If someone could help me understand whats going on (is it the clutch, compressor, etc) and what I ought to go about doing in order to fix it, I would apprecate it.

Here's a short video of the noise, Ac is on, clutch is spinning, engine is running ROUGH. Then I go inside the car turn the AC off, and everything is peachy, clutch no longer engaged. The main thing that baffels me is it still blows cold with it on! If my compressor was messed up wouldn't it not blow cold?

 

if it wasnt making noises before and is now starting, its probably on its way out. my brand new ACDelco r4 compressor made very similar sounds when new, and as i used it/wore it in, it quieted down... but if it was quiet and its starting to chatter its prob going to fail soon. I dont think its the clutch since i dont hear it cycling.

 

As per the blowing cold thing. Your compressor is making noise, but it hasn't completely **** the bed yet. The noise is impending doom. But, it's still pumping.
So yes, until it does blow completely it is still compressing and your still getting cold air.
HOWEVER, shut it off! Replace that compressor before it blows! once it blows, it'll send shrapnel throughout the system and the repair bill will at least quadruple.
Replace the compressor.

 

sounds like belt slap too on the bottom of belt. try tightening more and watch the slap.. it should also have a guard to stop belt from slapping the radiator hose.
Looks like original compressor, the clutch will cycle if reaches cold enough temps to prevent freezing.

not knowing history and mileage, kinda tough to say.. that clutch should not move if off..maybe on way out?

tons of threads on AC

 

Turn off the car. Check the air gap setting of the clutch. It seems too tight so even when the system cycles the clutch OFF its still dragging on the engagement slots inside. These compressor clutches are NOT like a engine to transmission clutch with fiber plate(s) dragging on a flat flywheel. The A/C compressors lock the pulley side of the clutch to the compressor side of the clutch using metal slots. It's either 100% locked together or 100% unlocked. Yours sounds like it is right on the borderline so its still dragging the face of the surfaces and grabbing.

To set the gap properly you need a special puller and installer tools and feeler gauges. Slip a .030 feeler gauge into the air gap between the clutch drive plate and the clutch rotor. Also, with the car OFF, you can put 12V positive to the clutch to make it engage then remove the 12V+ to disengage. This will show you the electromagnet works and how the clutch operates. When I do A/C work I always test the clutch like this BEFORE going through all of the effort of installing a compressor (this is a tip for others reading this).

The puller and installer can be borrowed from you local parts store. It's usually is a set of A/C compressor clutch tools for various brands but make sure it has both tools for the GM R4 type compressor. The air gap can be set with the compressor on the car without disturbing the refrigerant side of the system. Basically, using the special puller you need to pull the clutch plate away from the compressor just enough to set the air gap between the plate and the rotor to about .030".

Summary.....takes 3 seconds to slip a .030 feeler gauge into the side of the clutch head to check the air gap. All of the above is if that gap is too tight as I suspect it might be.

 

I think the clutch, on the front of the compressor, is starting to fail. If you watch the video, with the engine idling at a constant speed, you can see the clutch changing speeds (strobe action of the camera). The clutch appears to be "losing its grip" frequently.

The clutch can be replaced without losing refrigerant. Some A/C places will tell you that they have to evacuate the system....and THEIR procedures might require that, because they want to charge you as much as they can....but removing the clutch will not cause any loss of refrigerant in the system. Obviously, care must be taken to not damage any hoses or connections when you "release" the compressor assembly from its mounting; but replacing the clutch is do-able without dealing with the refrigerant at all.
If you call around to some A/C shops, you may find one that will change the clutch without messing with the rest of the system. It's worth making some calls to find out, I think.

 

Did you add any freon to the system? An overcharged system can act like what you describe.

 

I did not add any freon to the system. I think it is the clutch too, airgap is inconsistant. Car is in the shop rn for frame repair. I will take a look at the car when it comes back and see if the clutch is the issue.