A/C compressor is cycling even though A/C is off

[Danneman]

99 Yukon SLT. Noticed today that my A/C compressor is cycling, even though the A/C is off. Roughly every 18 seconds it goes on for roughly 6-7 seconds. Probably wouldn’t have noticed if it hadn’t been for that noise (that I can’t think of how to describe) that you hear at the front passenger’s feet when you’re using the A/C and for a little while after turning the truck off.

The compressor is fairly new, roughly a year or so - Delphi. Installed by dealer. Haven’t had any problems with it, it’s always been nice and chilly. No dye or anything on the unit, no obvious signs of anything wrong under the hood.

Any likely suspects I should look into?

 

[iCajun]

Was the HVAC control set to the defrost/defog position? If so, it should cycle.

 

[Danneman]

I'm getting the feeling I'm about to feel very stupid. Yes, it was set to windshield defrost/defog - but the fan was set to off. I have over my entire lifetime of driving always assumed that it doesn't matter where the HVAC position control is set, if the fan level is off then nothing is happening there.

 

[Cornelius98]

Compressor (A/C) runs to remove moisture from cab hvac box before it goes to your windshield.

 

[PG01]

Was the HVAC control set to the defrost/defog position? If so, it should cycle.

Compressor (A/C) runs to remove moisture from cab hvac box before it goes to your windshield.

^^^these

 

[Danneman]

Can't believe I didn't know that. Thanks!

 

[iCajun]

I read somewhere it is to circulate the oil and help the life of the compressor and seals over the winter.

 

[PG01]

I read somewhere it is to circulate the oil and help the life of the compressor and seals over the winter.

It Removes Moisture for defrosting windows