Thread: AC always on, cant turn it off

I bought an 04 GTP. The AC lamps is always on no matter what. It is running as on cold you can feel AC cold air. Anyhow, Can the switch alone be serviced? And, is this a common issue? (Note; it will go off when I turn the fan to off)

The ac lamp is lit constant no matter where the selector dial is set for feet, vents, defogger, etc. the only way to get the ac off is to turn fan off.

Yeah that's not right, I get what dsmuts means, anytime the defroster option is selected the AC will technically be on to remove moister and defog quicker, but the light should only be on when pressed. Maybe indicating a blown circuit? I'd take it out and open it up to look for burn marks/blown capacitors.

I forgot about this thread. Check your AC fuse, I don't remember which box it's in, but there's an obvious fuse box under the hood near the coolant reservoir and there's also one on the side of the dashboard. When you open the passenger door, it will be obvious, there's a panel you can pop off.

Also check to see if your AC compressor even engages.

PCweber, I have the same issue with my '05 Grand Prix. Today I took the car to the shop today to get the coolant and thermostat changed (car was not warming up fast in the cold weather) and the mechanic today told me it is the circuit logic board in the dash that is the problem. He said it would cost about $500 to replace the board (yikes!), so I'm probably not going to do that. So while he was changing the thermostat and coolant, he removed the AC relay to ensure the AC compressor stays off. The compressor is now off, even though the light next to the snowflake button on the dash is still lit! Your location says NE, not sure if that's Nebraska or New England, but either way it's got to be pretty cold where you are - so removing the relay is probably the cheap and easy fix for now until such time in summer when you need the AC again. Of course, doing this does compromise the defogging capability of the car in damp weather. I bet your issue is similar; let us know if you find it's something else.

I am probably going to try to wire up a switch to operate the relay independently of the dash switch in the spring when it's not so cold. That will be an interesting exercise and require some Yankee ingenuity.

I fixed mine. Went to the local "U Pull It" junk yard. Scrounged around in GM cars looking for HVAC control heads and tore them apart looking for ones with same exact momentary push swithes. IIRC i think it was 2000 & up Monte Carlo I found it in. I then desoldered and replaced the switch. fixed 100%. replaced them dam buls too at same time, they have them at radio shack.

Congratulations! So it was a bad push button switch, PCweber? I think I will go and do the same as you if that is all that is in my car. Could you briefly describe what you did to get to the switch, etc.? Does the earlier generation ('97 to '03) of GP have similar switches? Definitely a whole lot cheaper than paying $500 or so for a new board!

Just so everyone knows, I replaced the heater control unit on my '05 GP and that fixed the A/C always on problem. They are available on eBay used for about $40 or so, including shipping. Mine came off an '06 GP and it fit into the dash just fine. That was easier than taking the old heater control apart and desoldering and replacing the switch, but probably also more expensive. The momentary contact switches on these units seem to have issues after being repeatedly pressed numerous times! It took less than 10 minutes to swap in the new unit for the old.