Windows Won't Budge in the Heat

Dear Car Talk

Dear Car Talk | Apr 13, 2017

Dear Car Talk:

When it is extremely hot outside, the windows of my '97 Pontiac Bonneville will not go down. They always work in the morning, but not in the afternoon heat. Anything and everything associated with the windows has been replaced. This affects all windows. My mechanic is at a loss. It appears to be an electrical issue. Where do we start in an attempt to fix it before the summer? Thanks. -- Robin

I was going to suggest that you try cooling off the master window switch with a bag of ice, Robin. That way, even if it doesn't get the windows to open, you can put the ice bag in your lap and stay cool that way.

My real suggestion is that you make sure your mechanic has the car in his shop when it's actually misbehaving. So on the next really hot day, take it to him and park it in the sun with the windows up, and tell him not to look at it until after lunch.

Once he has the car and the windows are not working, he'll be able to do a bunch of very useful tests and narrow down the problem significantly.

He'll be able to see how far the current is actually getting. Maybe it's getting to the master switch on the driver's door, and that switch is bad; maybe it's not even getting as far as the master window switch.

He also can check any of the various ground connections that could cause the electric window motors to fail, or even run a temporary new ground to rule that out.

My guess, given that you've probably replaced all the obvious stuff, is that he'll narrow it down to something called the Body Control Module, or BCM. The BCM is a small computer that controls things like the windows, power mirrors, power door locks and climate control. It sits behind the glove box, under the dash or just on the other side of the firewall. He might even be able to find you a used one at a junkyard for $50.

But having the ability to test everything, while the car is in failure mode, will lead him to the answer. Or, if it doesn't, consider joining the Ice Bag of the Day Club, Robin. Good luck.

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