I have an 04 mach 1, auto. The a/c compressor is running whether I am on the a/c spot of the dial or any others, clutch engages and disengages just as it would if I actually turned the a/c on and air blows cold if on cold setting. any help would greatly be appreciated. thanks Brian B

 

Not sure if this applys to mustangs but when I had my 2006 Monte Carlo SS I had an issue kind of similar. Basically the AC would run on any setting and even when I turned the car off it would continue to run for a good 15-20 minutes before finally stopping. It ended up being the Blower motor resistor. Again not sure if this would apply to mustangs since I'm still learning them. But I know that was a pretty big issue with the Monte Carlo and impala of those years. You might check that.

 

if I turn the climate control off, the ac compressor turns off, same if I turn car off. its just when any of the climate control is on, at any fan speed, at any temperature.

 

Fwiw the ac is on in any of the defrost settings as well, does this happen on vent to?

 

yes all settings, vent, defrost, mix, floor, etc.

 

From time to time mine will do this, BUT if I change the air flow **** (Ie...move it from feet to face) it stops. The weird thing is I do not feel the AC unit disengage when I do this, unlike when I actually turn on the AC.

 

It won't provide a permanent or real fix to your problem, but in the meantime assuming you don't want the compressor to come on with all settings you could just unplug the 2 wire connector from the clutch.