My A/C compressor is engaging when on "Max AC", "AC", "Mix", and "Defrost".
Is it supposed to be running during all of those? I thought it would only run on the ones marked as "AC". If it is only supposed to run on the "AC" setting, how can I fix this? I can pull 16 MPG with my AC on, but I'd love some higher MPG to fix this.

 

The AC unit spins all the time, it's whether or not the clutch on the AC unit is engaged that matters.

 

It should come on in A/C mode and in defrost, helps dry the air out so your windshield won't fog during rain. So it is doing the right thing, besides unplugging it there is no way around it. You will notice a big difference if the A/C doesn't run in defrost when it rains, it wont clear the windshield as fast and it might fog up.

 

Will it still run if the heat is on? I use it to defrost in the winter.

 

Yes this is correct, the only time the compressor does not run is in "heat", "vent", and of course "off".
If I don't need to clear the windshield in winter, to keep the windows from fogging up in damp weather I turn my selector to Mix and crank the temp **** to what is comfortable and let her rip!!!

 

Yes (at least 10 characters)

 

He meant Floor and Vent. No position labeled Heat... not on an OBS anyway.

 

Yes, floor it is....... Goes to show that after 18 yrs I don't read the panel anymore.... I just know where to turn it to get what I want without really reading the markings.....

I guess I need to just shut up and leave it to the experts.....

 

I have a 460 and I can't even get 10 MPG with AC off

 

Don't be a hater daddylee100, my old '88 302 only pulled 8 on a good day.