I have a 99 Blazer with an odd AC problem. The air works fine as long as the engine is under load, but does not at idle or when you back off throttle at speed, seems like i read something about this on this forum with the TPS being the problem, does this sound right? Thanks

 

TPS shouldn't affect A/C. Does the compressor clutch disengage, or does the airflow change to defrost or change temperature? Need more information on what happens or doesn't happen.

 

Thanks Captain for getting back. The air works fine as long as the throttle is being pressed like, from a stop and getting up to speed, let up on the throttle even at speed the air will stop working, and i guess yes the ac clutch disengage, at a traffic light or a stop sign the ac clutch also disengage, i can hold the brake and press the throttle, while stoped, to say a 1k rpm and the clutch will engage. It is like as long as the engine is under a load the ac works fine. There is no change as in the the air vents, defrost, everything works as it should inside.

 

The clutch should cycle on and off, it is controlled by a pressure switch in the low side of the refrigerant system. There might be a problem with the switch, but more likely the refrigerant charge is low. Have you checked high and low side pressures?

 

I have not checked the pressure, it cools as it should as long as i am applying throttle pressure, or as long as the engine is pulling or under load like at cruising speeds, the clutch cycles at it should during this time, the ac clutch disengage when i let off the throttle and at idle and does not engage until the engine is under load again.

 

By any chance is there any belt noise such as squealing?
I still think it's low on charge though. Might want to check pressures at 1500 rpm and post them. Both pressures will constantly be changing up and down. Need high and low side pressures when the compressor clutch shuts off, and when it turns back on. Ambient temperature would be very helpful too.