QuestionMy car (see above) had a catastrophic failure in the a/c. We've had it replaced, but the compressor won't shut off. The only way to stop it is to turn off the car. We also replaced the, geez, I forgot what it's called. Maybe computer climate control? Please forgive me. It's the thing in the dash with the knobs that actually turns the a/c on. Anyway, the compressor still won't shut off. Any ideas?
AnswerVanessa,
This is the second time this question was asked to me in as many days. I find that shocking, because in all my time in the automotive a/c realm, I have never came across this issue.
OK, I am looking at your wiring diagram now.
Your A/C clutch gets its power through the contacts of your A/C relay from a 10A fuse located in the underhood fuse/relay box. There is also another 10A fuse that feeds the coil portion of this relay. With your engine on, if you pull either of these fuses at different times, your clutch should disengage. Does it? If not replace your a/c clutch relay. But I am fairly certain that it will. So that leads me to your next component. That is your Vehicle control module. This acts as the "brain" When several different processes happen and satisfy this, it will allow your compressor relay coil to find it's ground through your control head. For now I am going to assume that this is good, because the actual checks can be very in-depth and really should be done by an experienced shop. But a quick check... Locate your compressor cycling switch (on your accumulator-a canister roughly the girth of a soda can with two lines coming from the top)(this is usually located near your passenger side firewall close to your strut tower) This will have a dark green and a black wire plugged into it. Disconnect your plug. Did your compressor shut off? It should have. If it didn't... I'll get into that in a second. Assuming it did... locate your high pressure switch (This is on the rear of your compressor)(Make sure you shut the car off-you can unplug it with the car off and then start it again to see the results.) Safety first. It should have a Dark green wire with a white stripe, and a light blue wire plugging in to it. Disconnect this. This should also disengage your compressor. If neither your cycling switch or your high pressure switch being disconnected disengages your compressor clutch, that makes me begin thinking about your Vehicle control module being faulty. (or somewhere in your wiring something is grounded that shouldn't be)
But assuming your clutch disengaged, plug this switch back in.
From this point, the diagram heads into the cab and this involves many many sensors, some solenoids, and your Heater/ AC control module. Which I assume this is what you replaced. I am almost afraid to get into this over the internet, because it will get quite indepth, and many of the check points you will need to disassemble the dash to get to. I would highly recommend you take it to a reputable shop to have it trouble shot.
In a nut shell, your ac clutch relay is finding a ground somewhere in your circuitry that is causing it to energize its coil. Once its coil gets energized it closes the contacts and sends power to the clutch. Only the ground that it is finding is prior to all of the systems that are in place to shut it down. I would take it in to somewhere that you trust or have heard good things about. Or even, dare I say it, the dealer.
I am sorry for not taking you through the entire wiring diagram, but I hope you understand.
If you found this response at all helpful, please remember to rate this answer. Thank you fo rhte question and if I can do anything further now or in the future, please do not hesitate to ask. Good luck in everything.
