I''m having an A/C issue. My A/C, once turned on, will not SHUT OFF even if all of the switches are turned off. The other day I was driving on the freeway with the A/C on and when I exited and parked I turned everything on the dash A/C related off. I got back in it 10 minutes later and took off and noticed that the A/C was running as I could feel cold air coming out of the vents. I thought maybe it was just left over air in the vents so I kept driving... 30 minutes later I'm back at my shop and there is still cold air coming out the vents. The "A/C" button on the dash is NOT depressed-nor is it illuminated. The fan is on "0", and with the hood up and engine idling I can see the compressor clutch is still engaged. It finally froze my evaporator core and then the belt promptly popped off. So, now I have no A/C. I have not put the belt back on yet because I'm not sure what is causing the issue. I guess I need to start there. I should mention that as long as I don't turn the A/C on, it won't auto-run.. It's only when I turn it on, then try to turn it off that it won't release the compressor clutch.

My next step is to duplicate the problem, and then check the wires that cycle the compressor clutch for current. If there is current, then I know that something is wrong with the tune, the OS, or the wiring. If no current is present, and the clutch is still engaged, I will know it's a mechanical issue with the compressor.

Has anyone else had, or experienced, this problem before? It's a 411 PCM running the 12212156 (yes I guessed at the OS #'s so don't shoot me if I was off a # or three) OS. I did convert it over to electric fans which required removing a wire from the harness that used to cycle the MAX A/C door, and no longer using it (wrapped up inside loom). Could that have something to do with it?

 

A/C compressor clutch stuck "on"? When the engine is shut off, is the clutch still engaged even with the power to it off? With power off, use some thing to turn the engine over. If the A/C compressor turns with the engine, it(the clutch, not the compressor) is seized up

 

I thought so too but it does not engage the clutch UNLESS you turn the A/C on, then it does not want to turn off. I will figure out. I was just hoping someone had seen this before and could just say "hey, check this discombobulator and that will fix it". I always figure things out... The hard way! Meaning after I have it apart 2, or 20 times.. That's just the way it goes.

 

So shutting the engine off DOES shut it off? I was under the impression it was stuck on all the time.

 

No, shutting the engine off does not turn it off. The next time you start it, the A/C will still be running. I figured out that it has something to do with the MAX A/C or air recycling button. If I switch it over to draw in outside air, the compressor cycles on & off normally with the "A/C" button. If leave the switch for recirculation of air, it will then keep the A/C compressor running at all times.

 

Dumb question, but does it think the defroster is selected somehow? I know turning defrosters on will force enable A/C automatically. Just a thought

 

 

Sorry for the delay in getting back to you guys. I just put a new belt on, and the compressor does not engage or kick on any more at all. I now need to throw some gauges on it and check freon level. If the freon is good, I will just replace the compressor.

 

Sounds like the relay is stuck.