Lights that won't come on...

Dear Car Talk

Dear Car Talk | Jan 01, 1990

Dear Tom and Ray:

We have two 1986 Grand Am Pontiacs in our family, both of which have the same problem. In cold weather, when the headlights are turned on, the dashboard lights don't come on. A few miles down the road, they come on and stay on. Three mechanics have been unable to find the cause let alone fix it. It is disconcerting not to be able to read the speedometer. I would like to resolve this problem before it gets worse--are the headlights next?

RAY: You probably have a bad dimmer switch. That's the switch that controls the brightness of the dashboard lights. When it gets cold, the electrical contacts are probably shrinking and separating. After a few miles--after the heat comes on--they warm up, make contact again, and your dash lights come back. As long as the contacts stay warm, you're OK.

TOM: If you don't believe that things shrink when they get cold, Mae, reach into your husband's shorts next time he jumps in the ocean for a swim.

RAY: This shouldn't affect your headlights, since the dash lights are on a separate, parallel circuit. But get it fixed anyway. Have your mechanic replace the dimmer switch in one of the Grand Ams and see if that does the trick. In the mean time, borrow one of those miner's helmets so you can see the speedometer. Even after you fix the lights, you can still use the helmet for those midnight trips to the outhouse.

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