I had the hood on my truck up the other day while it was idling and noticed the A/C compressor cycle on, then off, then on. The heater controls were set to defrost, so I thought that maybe it was supposed to do that on defrost, as the dryer air the A/C puts out will clear the windshield quicker. Then I turned it to the heat just to see what would happen... same thing. The only setting the compressor wasn't turning on was the off setting.

Is this normal? Or is something messed up. The truck is a 98' 4.0L with auto.

 

The only modes the A/C does NOT run in are "Vent" and "Floor".

 

I checked and with mine the A/C compressor runs in all modes except off. I made sure that the temp control was turned all the way up too. Anyone else out there noticed this?

 

Its normal, I was told years ago that the compressor is made to come on with the defrost so that during the winter when the A/C is not used the seals and other parts will not go bad.

 

yes it's normal check in the manual.