A/C compressor noise in SC

Last weekend, my A/C compressor in my 81 SC (which has been updated to the new rotary type) suddenly started making an awful vibration/clatter noise, but only when the engine was revved quickly. I turned off the A/C and haven't run it since. In the sight glass on the receiver/drier the white ball is at the bottom. I assme this indicates the system needs a shot of refrigerant. Could low refrigerant be the source of the noise, though? Or might the noise be caused by something else (e.g. a bad compressor)? The belt is tight and the compressor is mounted solidly. Has anyone experienced this before? Thanks for any advice.

Darren Cooke

Hi Darren

You might want to take the belt off and turn the compressor by hand and listen for loose parts.

Was the system cooling when this happened, or do you know for certain that it is out of refrigerant? The little white ball should only move when the system is low on refrigerant.

If you had a bad leak i.e. a hose rupturing, then there is a chance that the oil in the system may have been blown out with the refrigerant. In that case, your compressor may be "dead"

When the new compressor was installed, was it changed from R-12 to 134-A? If so, then the oil should have been removed and new oil installed that is compatable with the 134-A. If that has not been done, then your compressor will suffer damaged.

Regards


Steve

Thanks, Steve, for your reply and advice.

The A/C was working fine (as cold as usual) when the noise started. In fact, it even continued cooling after that. According to the records I have, it was converted by the previous owner about 4 years ago to the new type compressor and to 134-A, and has been recharged regularly. Since then, the car has gone only about 8k miles.

I guess I don't fully understand how to tell if the system needs to be charged. You read it (watch the ball in the sight glass) when the car is running and the compressor is on, correct? Is it that if the ball falls from the top of the glass you are low on refrigerant?

Darren Cooke


[This message has been edited by dcooke (edited 06-19-2000).]

The sight glass is a device used to tell if your refrigeration system liquid line is full of refrigerant when it goes to the expansion valve. If it is clear when the a/c unit is running, than in all likelyhood the refrigerant charge is ok. If when the a/c is running and the sight glass is foggy (showing liquid flowing through it), then it needs to be charged. It doesn't sound like you lost your refrigerant.

Also another way of checking is to feel the line coming from the evaporator back to the compressor - it should be cold and sweating.

My recomendation would be to take it to a a/c shop and have them check it out. They have all the proper tools to do an evaluation on the system - refrigeration gauges will tell you what the system is doing.

If the pressures on the system are off when you increase the rpm of the engine, then the compressor has a problem.

Are you sure there is nothing loose ratteling around by the compressor to make you think it could be the compressor? Anyway I think it would be wise to have it checked out.

Steve