Strange AC issue

[Adanesahde]

I have a 97 Mustang GT and am having an odd gremlin I can't seem to figure out in my AC system.

For some reason, the AC compressor will NOT disengage under WOT. It spools up all the way to redline without disengaging (I can tell not only because of the sluggish acceleration when the AC is on, but it also whines like a banshee when I give it throttle). The AC system works great and cools just fine, but I'm concerned this is going to wreck the compressor in short order. My understanding is the AC compressor should switch off under hard acceleration then back on at steady throttle.

I've scoured google looking for information on this, but everything I can find is based on the folks having the opposite issue. Has anyone ever heard of something like this and have any idea on where to start?

 

[Adanesahde]

I should also note, I know the compressor clutch works isn't just stuck engaged because I tested the low pressure sensor input and the compressor was disengaging like normal for that.

 

[Noobz347]

It seems like you've verified that the A/C clutch relay is working.

That leaves wiring and/or a pretty good chance that your ECU requires repair since it is responsible for tripping the relay.

Home - ECU Exchange

ECU Exchange specializes in the re-manufacturing and repair of engine control modules.

www.theecuexchange.com

 

[Adanesahde]

It seems like you've verified that the A/C clutch relay is working.

That leaves wiring and/or a pretty good chance that your ECU requires repair since it is responsible for tripping the relay.

Home - ECU Exchange

ECU Exchange specializes in the re-manufacturing and repair of engine control modules.

www.theecuexchange.com

Hmm, it is on a custom tune since I have it supercharged.... I wonder if my tuner just didn't account for an AC in the tune.

 

[Noobz347]

Hmm, it is on a custom tune since I have it supercharged.... I wonder if my tuner just didn't account for an AC in the tune.

Also a possibility.

 

[Mcmahst]

I’m wondering if you could rig a test of the WOT relay by taping into the relay and attach a light circuit that you could visually verify if at WOT the ECU is signaling it to disengage the clutch? Just a thought to narrow the issue.

 

[Adanesahde]

I’m wondering if you could rig a test of the WOT relay by taping into the relay and attach a light circuit that you could visually verify if at WOT the ECU is signaling it to disengage the clutch? Just a thought to narrow the issue.

That relay is inside the fender on the front passenger side, correct?

 

[Mcmahst]

You know, I’m not sure, but I know folks on this site know.