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Crazy Climate Control

Q. I am having problems with my AC. It blows cold air fine but it won't blow the cold air all the time. It just started recently. It is a SSEI supercharged engine and has climate control. Recently, when you start the car, the outside temperature on the AC display flashes for a minute or so then stops flashing. The only thing that is consistent is that it blows hot air when it is hot out and blows cold air if it is cool.

My brother-in-law thinks it has to do with the doors that allow the cold air to get inside the car. When it decides to blow cold it will freeze you out. Have you ever encountered this type of problem and what do you think it might be? I have had problems with my dealership taking care of problems so I don't trust them. Would like to get an idea what it might be before I take it in or if it is something I can repair myself.

A. Automatic Climate Control (ACC) is a very complex system. It's controlled by a computer and links to several sensors throughout the vehicle. It get's it's inputs from these sensors and in turn controls the A/C compressor, heater control valve and vent doors. Since the system is vacuum operated and your vehicle is supercharged, there is a vacuum pump located in the engine compartment to supply the vacuum the ACC needs to work.

The computer has a self diagnostic feature that will detect a fault and store a trouble code when something goes wrong. When you start the car the computer tests it's inputs and if all is well, it does it's job. If it detects a fault, it will tell you it has found a problem by flashing the temperature display. A Technician can put the computer into a diagnostic mode and extract the trouble code and then be able to fix the problem.

It is difficult to diagnose a system like this because it is so complex. I suspect the problem could very well be a door problem since that's the most common thing with an ACC system.

What you can do is get a diagnostic manual and it will tell you how to put the system into diagnostic mode and then you can pull the code and reference it it the manual and see what it is. If you can't find one in the auto parts store, go to your public library (the main branch if possible) and they will have manuals you can use that will have the information you need.

Is it something you can do yourself? It's not something I would want to do. If it is a door problem then it would involve removing the heater box which can be a two day job. It requires removing the dash board and can be a mechanics nightmare. Hopefully it will be a bad sensor somewhere, and I hope it is, but the chances of that are slim.

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Additional Information provided courtesy of AllDATA and Warranty Direct
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