Hi,

I was driving to work today and turned on the heater as it was raining and the windshield began fogging up (was only for approximately 5 minutes). When I pulled away from a stop sign I heard a belt sound squealing and could smell the smoking/buring smell. I popped the hood at work and noticed that when the heater is shut off all apears well, but when I turn on heater or air conditioner it begans to squeal. It then will start smoking. It appears to be coming from the belt attached to the ac compressor.

It is a 93 caprice classic ls- in excellent condition...minus this problem. Any help to identify the specific problem would be greatly appreciated.

thank you

Shut off the engine and allow to to cool to a point where it is safe to touch. Open the hood, grab the AC compressor clutch plate, and try turning it by hand (both directions). If you can turn the clutch plate at least one full revolution in both directions, the AC compressor is probably O.K. If you cannot turn it fully one revolution or more in both directions, the AC compressor may be locked or internally damaged.

If the compressor turns (there will be some resistance, but it should turn) the belt, any belt tensioner(s), and sheaves are suspect. Make sure the belt is clean, not contaminated, and snug.

I would go with the idea of the compressor causing the problem. The compressor has an electric clutch that causes it to engage the belt when you need the compressor (such as running AC). When the compressor is not needed, the clutch disengages. Since your having problems only when the compressor is running, that would indicate the clutch engages, but the compressor will not turn (could be bearing failure or something else causing a locked rotor).

It has to be the compressor clutch locking up. The AC compressor will run when you turn it on to defrost. It's to help remove the humidity from the air blowing on the windshield. Follow the above suggestions. They are spot on.

Thanks for the info! I does make logical sense about the clutch not working properly. And I did not know the compressor ran when the deforst was on - thanks for that info as well. If the the clutch is shot would the AC compressor would need to need to be replaced, or only clutch itself. I am assuming a compressor would not be cheap, unless I could find a used one - and there are not many of these cars left in the junk yards in my area. It has the L03 - 305.

Thanks for the info! I does make logical sense about the clutch not working properly. And I did not know the compressor ran when the deforst was on - thanks for that info as well. If the the clutch is shot would the AC compressor would need to need to be replaced, or only clutch itself. I am assuming a compressor would not be cheap, unless I could find a used one - and there are not many of these cars left in the junk yards in my area. It has the L03 - 305.

Don't automatically assume the compressor has failed. Try turning it first.

If the compressor has failed, you can get a used one, or a reman unit for $149. Considering that a new/reman clutch is $110, a reman compressor is cheap by comparison. If you find it is only a clutch, it can be replaced on the vehicle, without having to recover the refrigerant charge. If the compressor has failed, the refrigerant needs to be recovered, the system evacuated after assembly, and new oil and refrigerant added. At that point, it would only be prudent to check the expansion orifice tube and run a system cleaner through before the evac and recharge. The cost of that alone makes the use of a junk yard compressor risky, since any failure is going to require another evac, flush, and recharge.