Thread: AC not working on settings 1 - 4.

I own a 1997 Grand Prix 3800 SE and when the AC is set on 1 - 4, it does not work and also turns off the head lights. It works on setting 5. I have spent a lot of money trying to fix it with no success. Does anyone know what I need to do to fix this problem?

Would that cause the headlights to turn of?

I took it to Ice Cold Air this week. ( A trusted mechanic). They replaced the resistor or a relay switch, because they thought the same thing as you, it appears. It didn't work. They advised me to take it to a GM dealer because it must be a wiring harness/computer problem, that they might be familiar with. I have an appointment Monday with GM dealer, but they want $175.00, just to hopefully tell me what is wrong. I have spent over $1000.00 trying to fix the AC. I appreciate your suggestion. I guess I am grasping at straws hoping to fix it without GM.

You can find the short if there is one with a multimeter and some patience.

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The blower resistor has been changed twice and I had a new ignition switch put in quite a while back for a completely different reason. I am now wondering if that is when the problem started. Not sure of the time line. Could it a ground problem caused by the ignition switch?

That I don't know. Is that something I can check myself in the fuse box?

Yes you can check it yourself.

Also, FWIW, I had the same issue myself, it was the ignition switch. 85 bucks for an AC Delco brand replacement off of Amazon, plus a YouTube video and I had it replaced in less than 1.5hrs.

I'm starting to think the same thing. Like I said I replaced the ignition switch for a different reason a long time ago. That could have been the start of my problems. I guess now it's a process of elimination. Thanks for your input.