A/c won't staying on

[legnd99]

I have a 02 and realized the other day that my ac is coming on when I put the control knob on vent/floor, floor then of coarse defrost/floor and defrost. But acts right when on regular vent. It is killing my mileage I went from around 22 to 18 then finally the other day heard it when left truck running and got out.the blend door seems to be acting right and I get cool air when in cool zone and hot air when on heat. Just compressor runs when it don't need to.

 

[Markaprice73]

http://www.explorerforum.com/forums/showthread.php?t=316194&highlight=compressor ..read ncranchero's response. Also, with "winter gas" you will see a 1-2mpg loss. IIRC the compressor runs at first start for a sec or so in some selections(cant remember the ones)(the ones you think that dont need the compressor)to keep the seals lubed. Not sure what that means.
Also..(i copied this)
MAX A/C - The compressor will operate if the outside temperature is above 43 deg. F.
A/C - The compressor will operate if the outside temperature is above 43 deg. F.
PANEL - The compressor is off.
OFF - The compressor is off.
PANEL/FLOOR - The compressor will operate if the outside temperature is above 43 deg. F.
FLOOR - The compressor is off.
DEFROST - The compressor will operate if the outside temperature is above 43 deg. F.