AC On All the Time, 2005 Pontiac Grand Prix

[raffy]

Hello everyone! I just got an '05 Grand Prix and the AC light is always on. When I push the button to turn off the AC, it stays on. The AC seems to actually be on as well when the fan is on, and far as I can tell the AC is working (it is rather cool here so can be hard to tell but cold air definitely comes out unless I crank up the heat). Since there ia a button for the AC on the dash, I assume it was designed to be turned off. So what is going on here? Is it a relay, bad switch, or what?

Thanks in advance and Merry Christmas to all of you!

 

[rshaw125]

Until you solve the problem pull the AC fuse.

 

[NHGUY]

You could also unplug the compressor clutch or a pressure switch,that would kill AC as well.A fuse (if it uses one) would be easier though.

 

[crw]

One place to look might be the blower resistor. I don't think it's that, but something to think about.

 

[JTK]

Given the vehicle is new to you, are you 100% you don't have a HVAC option selected that keeps the a/c on? Some of the fancier systems will run the a/c more than you might want.

Other than that, maybe a relay is staying pulled in, when it shouldn't?

Joel

 

[dishdude]

If the controls are set for recirc, mix or defrost it will run the A/C compressor.

 

[mechtech2]

Yes - the AC is 'ON' in many vent positions, not just AC On.
Defroster , defroster mix, vent and floor, all may turn the AC on.
In other words, there is probably nothing wrong.

 

[raffy]

I tried removing the A/C relay fuse, and that did nothing (A/C light still on and compressor still running). Then I put the fuse back in and tried removing the A/C relay itself. A/C was still on even after that, which I found to be really weird. What's the point of having a relay when it's on all the time?! I did not try to remove BOTH the relay and the fuse; I'll try that and see if that does anything.

I don't think it is supposed to work that way. There is an A/C button on the dash and that should turn the air on and off. Nothing I've tried gets it to turn off. I'd rather not have it running when it's cold here and it also reduces gas mileage somewhat, I'm sure.

 

[eljefino]

You can see if the compressor is coming on, the clutch is a doohickey with a triangle and three circles (usually) if it's clutched it spins with the pulley and if it's off it just sits there so you can see it.

+1 on the pressure switch disconnecting. You can also feel the metal pipes to see if they're hot or cold and if humidity is condensing on them.

 

[raffy]

The compressor is coming on. My question is, why is A/C button (the one with the snowflake on it) not turning the A/C off when I push it? Surely that button would not be there if the A/C was meant to stay on all the time.

 

[eljefino]

Maybe there's a shorted contact in the Defroster/feet/face selector that's telling the system it's in Defrost when it's not.

 

[raffy]

OK, here's what I found out. After taking the car in to the shop to get the coolant and thermostat changed (separate issue, car wouldn't warm up fast in the cold weather we've been having), the mechanic told me the logic board that controls the AC is bad and would have to be replaced (to the tune of $500 or so) to fix the AC always on issue. So what he did was remove the AC relay and it actually did stop the compressor from running, even though my AC light is still on. So I'll keep the AC relay out until it starts getting really warm again in late May or early June and maybe jury rig some wiring and a separate switch in the cabin to manually turn the AC clutch on and off - not going to spend $500 to get the board replaced!

I hope this is helpful to anyone who might have a similar issue.