I still have not found the problem with my passenger brake light/3rd light. There is no power to either and according to wsm the 3rd brake light gets power from passenger side. (this is on a '86.5 auto). Driver side works fine.

The problem started after intake refresh. Both antilock and brake light warning was on. Push reset on center consul and '!' goes off but both warnings stayed on in cluster. I have disconnected plug on passenger side and no power. Thinking maybe wire broken close to area removed sheathing and tried further up harness, still no power. Using a stick pin bridged the driver side to passenger side and both lights worked. When bridged the warning light in cluster is still on. However now the antilock warning is gone and main '!' does not light up when key on or started.

Before I start slicing the harness all the way to the front of car, is there any point along the line I should address/look at first? Also have tried different bulb check unit with no change. Checked brake switch and is good. Should the fuse panel be the next place to look? I do not think fuse is at fault as it is good, but does wiring go through one of the busses on bottom? If so which one? Is there an area where harness is more likely to have problems?

I really need some help on this and admit I am not real good at electrical, but would really like to drive the car. HELP!

 

From Terminal 54R on the Bulb Check Unit, a black wire with a red stripe runs to T10, a six-terminal connector, where it joins (at, but not thru T10) a black/red wire that runs to the right brake light, and also goes thru the connector to a black wire that at the next connector turns back into a black/red wire that runs to the center brake light.

Check at Terminal 54R for power with the brakes and ignition on. If you have power, the problem is at the connector or in the wire from 54R to the connector.

Connector T10 is located behind the passenger trim panel, low, just behind the passenger door.

 

Thanks for the reply Wally. Found a short on the black ribbon wire for the 3rd brake light. Apparenty the ribbon was rubbing and short was not found until harness was removed from hatch. It was hidden pretty well. Can such a short ruin the controller? I have another from earlier car but not sure if it will work.

 

No idea whether the short to ground would kill the bulb control unit - doing the tests outlined above would tell you.