Sunday, October 28, 2007

Dad, My headlights don't work

That was Thing1 a week ago when he called home one night. He had gone out to his car to go somewhere and he had no headlights. Parking lights were ok, DRLs worked, and so did the high beams. But the regular lights did not. He replaced the bulbs and checked the fuses - nothing. Since he was coming home in a week I just told him not to drive at night and I'd take a look at it when he was home.

I did some research on his car and found that this is a common problem on late 90's GM J body cars. At least there was some hope of a simple solution :-). The solution was either the headlight switch, a bulb socket, or a wiring fix.

So yesterday I started poking at the car. A check of voltage at the sockets show 12.8 volts with the lights on. That seemed ok so I ruled out the switch. No obvious scorching on the bulb sockets or adjacent wiring. Ok - its probably on of the junctions that are ~1 foot from the battery. So I grab the DVM and check continuity between the positive and negative leads of the regular beams. Positive was 0 ohms. Negative was 1.3 Meg ohms. Thats bad. Thats wiring.

So I started to unwrap the harness going across the front. Got the the junction area and no problems with the negative wire. In fact there was no junction for it. Hmmm. Then I looked closely at the negative wire from the drivers side. It headed in the harness over to the passenger side rather than back to the firewall socket. So I unwrapped the passenger side of the harness a bit and counted wires. Compared to the drivers side there was 1 less. And it was the color of the negative wire. There was another junction somewhere. So I unwrapped the center of the harness. In the middle of the car, right by the hood latch, there was another splice. This was for the negative lead for the low beam lights. And it was corroded. By the time I got it unwrapped it fell apart.

In a effort to clean things up I unwrapped the whole harness and cut back the corroded wire about 6 inches on each end. A little bit of spare wire, solder, and heat shrink tubing and the lights were on. Took some electrical tape and re-wrapped the harness. 4.5 hours after I started it was done. Just in time for cake! Smiles all around.

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