Electrical issue?

[glhs571]

Hi everyone, car is a 1988 CSX-T. When I press the brake pedal my third brake light stays stuck on and rear window defrost is turned on simultaneously. Has anyone had this strange issue occur? Thanks

[Vigo]

Definitely a short to power, the question is where. Alldata's diagrams for this car are kind of shitty which is making it hard to tell where the two circuits come close to each other or pass through the same components/connectors.

The power for the CHML (3rd brake lamp) comes from a 20 amp fuse (#6) and goes through a 2-terminal connector under the dash, then to the brake lamp switch at the brake pedal, then BACK through the same 2-terminal connector, then to a connector under the steering column where it is spliced on the same side of that connector to a white wire which goes through a connector on the left side of the instrument panel (which the power for the glass element also passes through on a different terminal) before heading down to the floorboard and travelling along the sill plate to the LR quarter panel area where it goes to a 2-terminal connector high on the LR C-pillar which has the power and ground for the CHML. It then goes into the flex tube going into the liftgate where it goes to another 2-pin connector inside the liftgate that goes to the light itself. The ground for the heated glass element is spliced/shared with the CHML ground between those two connectors.

My educated guess is that the two power wires for the CHML and heated glass element are rubbing together where they go from the body into the liftgate because that area flexes whenever you open the liftgate. I would have someone hit the brakes or lean something against the brake pedal and then go back and wiggle the wires between the body and liftgate to see if you can get the glass element to turn off. If you can, then you'll have to tear into that area and repair the damaged wires.