might need to reset the problem indicator
it is probably the bearings going out in the ac compressor pulley or belt slippage. the reason it is different when it is on is because the belt is not under "load" or has resistance.
The ac compressorThe ac compressor
look for the ac line going in to the compressor or the port on top of comp
the ac belt or the compressor bearings are going bad
Assuming you are asking about the ac compressor, there would be two possibilities, blown fuse or low on freon.
you have to remove neg.batt cable for 1 minute.may have to do a couple of times to reset ac controller
If the AC compressor is engaging it could be the heater control valve is stuck open. If the AC compressor is NOT engaging you probably have a problem with the controls, a sensor or the compressor.
It is possible the air compressor is bad. You will need to replace the air compressor, so the air will work again.
You have to go on the compressor! My husband has a 95 and the auto parts manager told him you have to.
It is on the top of the ac compressor.It is on the top of the ac compressor.
chevrolet and other GM use the HR100T AC compressor