97 lesabre tail lights out

Neighbors 97 lesabre tail lights are out but the bulbs and fuses are good. All brake lights, reverse lights and turn signals work. Suspect a grounding problem or short in the wire harness. Anything else that I should look for on this car before starting the surgery. Possibly a TSB etc..

The taillights and brake/turn lights are provided by two seperate circuits but within the same bulb. The bulbs lighting the tail/brake/turn have two filiments in them, dim and bright. (Just basic "tail light operational theory" strictly for FYI purposes.)

I suppose it's possible they burned out the dim filiments in both bulbs and the burned the filiments in the center "taillight only" bulbs.

But to do that, they should of blew a fuse. Likewise, if there is a grounding short between the front of the car and the back, they also should of blown a fuse.

Confirm fuse 8C (10A controlling Park, Tail, and Marker Lights fuse on 96-98 Buicks) with a multimeter.

If fuse 8C is good but the tailights, foward parking lights, and side marker lights do not illuminate... Then the Pink, Orange, or Brown wire providing voltage to fuse 8C from the Light Control Module is bad. Check voltage on slot 8C with a multimeter or probe with the headlight/parklight switch on.

If the tail lights are not working, the forward park lights (dim turn signal) and side marker lights should also not be working. If those lights are working and only the tail lights are out, then the Brown wiring running to rear of the car is most likely severed inside the wire loom (preventing a ground short that would blow the fuse).

Beyond that, other possibilities. Fuse 6C (25A) and a 20A Circuit Breaker provide power to the Light Contol Module. They could be faulty. There could be a short in the wire coming from the 20A circut breaker, causing it to continuously trip and reset. However, these senerios should also kill the head lights. If it involves a problem with a Light Control Module, most likely is it an internal problem with the module, it may need to be replaced...

There could also feasibly be a relay that has gone bad. Still provides power to the forward park lights, but not to the rear. However... it would be a strange for a relay to seperate the circuits like that. Due to the fact that the tail lights should exist on the same logically continuous circuit that provides power to the front park lights...

BTW, what do you mean by TSB?

Thanks for the quick info I'll follow up. TSB is a "technical service bulletin" that car manufacturers issue for post production problems so that service techs can fix them if customers show up with the same problems.

Just following up with the cure. Good call Avatar307. It was the 8c fuse. My elderly neighbor missed it when he checked them. All's well now.