heater kicking idle up and down

curts2500 · September 9, 2004

can hear heater clicking on and off, under the hood. idle up and down. What's causing this??

budhayes3 · September 9, 2004

If you're climate control is set to AC or Defrost, the ac compressor will cycle on and off and the computer will adjust the engine idle up and down to compensate for the extra load from the compressor.

If that's the case it's normal. If it's surging like crazy, then that's another thing, need more info.

curts2500 · September 9, 2004

notice it in morning when running defroster. cycles every 5-6 seconds. haven't noticed it until recently.

budhayes3 · September 9, 2004

There is a possibility that the ac system is low on refrigerant, causing the compressor to have to cycle on and off more frequently. Is the ac cold?

curts2500 · September 9, 2004

Can I assume this could be verified(low refridgerant) by unplugging compressor?

budhayes3 · September 10, 2004

If you unplug the compressor it will just stop running...the best way to check for low refrigerant is with a set of guages, if you know anyone who has them. I don't believe that GM uses a sight glass, or that would make life real easy. Just fire up the AC and check the sight glass for excessive bubbles.

You could find the low pressure switch (I think it's on the accumulator, but I'm not completely sure) and jump across it and that should allow the compressor to run...but don't do it for too long. If you are low on refrigerant and you run the compressor excessively it could be catostrophic to the compressor.

It sounds like the refrigerant is low, but it's hard to tell without actually experiencing what the vehicle is doing. Your best indication would be the ac operation...does it get cold or just cool? If you feel that the ac performance has dropped off, then you more than likely have a slight leak in the system.