Thread: A/C Always On

I am a newbie to GP's, just got an '05 a few days ago, so just getting familiar with it. It is well used with 154K miles on it; it seems to run and drive pretty well. I noticed that the A/C seems to be always on. When I push the A/C button on the dash, nothing happens and the light next to the A/C symbol remains lit unless I turn the fan completely off. Is this caused by a bad switch, or a bad relay, or something else? As far as I can tell, the A/C does work and I can get heat out of the vents by cranking the heat knob up. It is pretty cool outside here though now, so can't tell 100% for sure if the A/C is really cold or not, but cold air does come through the vents when I crank the knob over to the cold region.

Any help is greatly appreciated! Great forum here!

Before anyone else makes this mistake (are you the same guy that posted this in the 04+ specifics section? If so sorry you're still having problems!), the A/C does turn on when the selector is on any mode that includes the windshield defogger. This is to remove moisture from the incoming air to defog the window quicker. HOWEVER, the A/C light shouldn't come on for this mode, and something is indeed wrong if yours is constantly lit.

Check to see if your A/C is on while not in defog mode, and if clicking the button (regardless of indicator light) still engages/disengages your A/C. You should notice a change in RPM every time you hit the button. Then we'll go from there. It could be a faulty relay causing it to always signal the A/C on.

Nik, no I'm not the same guy who posted in 04+ Specifics. I went over there to look and his problem is exactly the same as mine! I am not on defrost mode so that is not what's causing it. Someone suggested looking at the AC fuse; I'll go ahead and check that out. If that doesn't work, then maybe I need to look at the AC relay as it's probably stuck on. The AC compressor does seem to cycle on and off so the system seems to be working as far as I can tell. It is too cold outside now to tell if it is really cooling, though! At any rate, I would like to be able to turn the AC off and on, if for no other reason than to keep it from fighting the heat. Thanks for your help!

OK, I tried to remove the A/C compressor fuse and the compressor is still on whenever I have the fan on. Then I replaced it and removed the compressor relay itself. Compressor still runs even without the relay! Very strange indeed. And I know the compressor is running because I can detect the slight RPM increase when it's on. I'm pretty stumped now. Any ideas? I guess I could try removing both the fuse AND the relay, but I doubt that will make any difference.

OK, here's what I have found out. Pulling the relay does indeed stop the compressor from running. So I will keep the relay out until summer. I took it to the shop to get the coolant changed and a new thermostat (it's too cold outside now to do it myself!), and they told me that the logic board behind the dash is kaput and would need to be replaced to fix the light always being on (and the compressor running when the relay is installed). Naturally a new logic board would cost $500 or so, so I'm not going to replace it! I may jury rig some jumper wires to a switch to be able to manually turn the compressor on and off and allow the relay to be installed, but that will probably be a project for the spring!

I hope this is helpful to others who may have a similar issue. If your A/C compressor is always running and you can't turn it off by pressing the button on the dash, one possible cause is a faulty logic board.

Maybe "logic board" is not the best term to use, although I thought that's what the mechanic said! The Haynes manual shows a "Heater and A/C Control" board in the electrical schematic that covers the A/C system, so that must be what he was referring to. It has some solid state electronic components in it, so in a sense it is a logic board in that it processes user inputs and is supposed to provide certain outputs if it is working properly. Apparently these things are pretty expensive; it might be possible to get one from a salvage yard more cheaply but I think I'm going to go the cheap and redneck route and wire in a switch to control the A/C compressor.

Looks like PCweber figured out how to fix it on his thread over in the 04+ Specific forum. I'll probably try to find a "new" used AC switch at a junkyard, pull off the center dash and replace it using the soldering iron. It appears to basically be a bad momentary contact switch.

OK, after a long while I finally fixed the A/C always on problem. I received a used heater control unit (which is the unit on the center dash that has the three knobs for the fan control, vent settings and heat control) from a business on eBay and installed it today. Basically I removed the center dash cover panel (using nothing but my fingernails), disconnected the wiring harness for the digital odometer, removed the starter switch trim piece (also with my fingernails) and then unscrewed the heater control and the cubby hole below it (four screws). I then removed the heater control wiring harness and attached it to the new heater control and then reversed the above procedure to button everything back up. Your mileage may vary on what you need to get the center cover panel off; you might need a plastic putty knife or something (don't use metal as it will probably scratch your dash).

I tried to find the heater control at junkyards but didn't have any luck finding a decent 2004 or later GP with the exact same heater control I have in my car. So eBay basically saved the day for me, for $40 and a few minutes of labor I can now turn my A/C on and off from the dash. Yee haa!