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Please help me! Major A/C problems-2008 Pontiac G5

I have had my 2008 Pontiac G5 since 2009. I got it used with about 32000 miles and it currently has 110,000 miles. It is the basic model G5. I love my car and want to keep it for a long time. It is in great condition except for one problem: the A/C. So it basically only will blow out heat, even if I have everything off. Sometime if I turn the knob quickly from Cold to hot to cold I will get some cold air but only for a few minutes. The thing is I just can’t turn it off as it is always blowing out some hot air which makes my car miserably hot in the summer. Also when it does blow out cold air, the fan is weaker then with hot air. All these issues have gotten progressively worse over the last few years. It used to be that at times I would have A/C for long periods of time when I did the rapid spin of the knob but now the spinning of the knob does not even work. I have had many repair shops look at it and spend well over $1000 to get it fixed but nothing has worked (people have tried new Freon, fixing the door part that flips from hot to cold,etc.) What could be my issue? Please help me as I want to keep my car but making any long trips is very difficult in any weather above 75 degrees as the car becomes a sauna. O yea did I mention that I have had this problem for the last 4 summers and just want it fixed already! I want a car with A/C, please help me!

Well you really need the factory manual with the troubleshooting charts and a HVAC technician. The first thing I’d suspect would be the whole heater and AC switch module in the dash. Rockauto has the whole shebang for around $100. Don’t know if it still uses the HVAC programmer module anymore or if the switch module takes its place. When you go to AC, does the compressor come on so its just a blend door issue? Or does the compressor not work at all? If the compressor doesn’t work there are simple checks to make sure all the electricals are ok such as the low pressure switch, but I suspect you need to replace the whole dash switch.

Doesn’t appear to be a HVAC programmer used so the control unit can be ordered from or for $133. After years of frustration and $1000, I’d just put a new control box in to try.

I can not hear if the compressor is going on. I only get A/C rarely. It does typically blows out hot air all the time, even when I have everything in the off position. Does this make a difference in your diagnosis and recommendation of replacing the whole control unit? How much does this cost to repair (I know in the past I needed my whole dash to come off and that was so expensive)?

I had some people also suggest it could be an electrical problem, and that it could be the electrical controls just thinking I always want heat. Does that seem plausible? Could that be checked easily?

I also had someone said it could be the actuator in the HVAC control, if I were to put a whole new control box would that help if the problem & fix my issues?


The switch module IS the whole control unit. There is no control box. Look at the picture. Its all the knobs blow the radio that controls the settings. Pull the trim panel off and install. The only other parts are the blend door actuators but you said that had already been replaced. You can look at the diagram at gmpartsclub.

You need a set of gauges to install on it. It could be just a high pressure switch cutting off AC. Could be a number of different things and could be cluster. Cluster does make sense. Did you see if compressor comes on and off. Is it getting power to AC clutch when it quits?clutch windings could be weak and not able to hold clutch in. It just pulls in and is unable to hold it engaged. Need to know if pressure switches are closed or not. Up to you but you would want to troubleshoot it before you just go buy a cluster.

There are shops that specialize in air-conditioning repairs. Have you tried one of those or just general mechanics?

Well the clues are that they already tried charging the system. They wouldn’t have done that if the compressor wasn’t working and they sure would have checked the pressure switch, I would think. The other thing was that he said they diddled with the blend door and had to take the dash apart to do it. Also by spinning the control used to sometimes make it work.

There’s really not much left on the system except the controls. Given he’s already spent $1000 on it, it sure would be worth a hundred dollar part to me, which should have been checked out at the start. Obviously a dealer didn’t look at it first.


Cannot argue with that logic at all. Agreed.

You can go to a hardware store and get a ball valve and a couple of hose barbs and put it in one of the heater hoses under the hood. This will stop hot coolant from getting to the heater core under the dash and that will at least keep from adding heat. Then you can work on the AC which is suspect is working but has been overwhelmed by the heater.

Concurring with @lion9car above about using an AC specialty shop. Or at least an inde shop or dealership that specializes in GM cars and has someone on staff trained on the details of repairing GM AC systems. AC systems for cars these days are especially non-forgiving. The old days of just putting in some more coolant when the AC doesn’t work are long gone. The coolant charge is much less now than in the past, and putting in more when more isn’t needed can do a great deal of expensive-to-fix damage. Unless the OP is prepared to find and read the factory service manual for the procedures, buy the necessary specialty tools and equipment, I think the best plan of action is to seek out someone with the proper GM AC knowledge and experience.

So how do I – an inveterate DIY’er – deal with this problem? My solution, I don’t have AC in either of my two vehicles.