AC compressor turns on for no reason

[freak]

2000 4wd XLS 4.0 OHV 5sp

I've been having a problem with the engine idling too high somewhere between 1500-2000 rpm. I've gone nuts trying to find a vacuum leak but cannot locate one. Anyway... I noticed today that the engine revs up when the AC compressor turns on. Problem is that the AC is not on. It is NOT on defrost either. The heat was on and the dash switch was on a mix of vent/floor. Why would the compressor turn on when the switch is on vent/floor?

 

[doubledflooring]

it comes on with the heat in the winter to take out the moisture and dry the air as it heats the interior

 

[dogfriend]

If your 2000 is like the 97 (I think that it is), the A/C compressor can come on in any of the Heat or A/C modes except for Vent and Off. You can find this in the owner's manual.