I noticed my high mount brake light (the one in the spoiler on top of the rear window)comes on sometimes without pushing the brake pedal,but goes off when you do push the brake pedal.Also noticed when this happens my defog switch lights up dim,so I pulled the defog relay under the dash and my high mount brake lamp went off.Im wondering if the rear defog and brake light use the same ground point,since the brake light is obviously getting power.Car is a 91 Civic Std hatch.Anyone have an idea?I had a Helms but sold it when I sold my CRX so now wishing I hadn't.

 

Update...went to the local pull a part today and got a defrost relay and switch.Swapped them out and now my defrost turns on and off like it should,BUT when the defrost is on my high mount brake light is on.Hit the brakes,and it goes off.Wiring looks to be unmolested,so I have no clue.If it makes any difference,my reverse lights arent coming on.All fuses appear to be good,and my regular brake lights just above the bumper work just fine.

 

UPDATE:The problem turned out to be two broken wires in the rubber boot at the top right corner of the hatch.Theres a black/green,white/green,and black.The black/green is the defrost power,white/green is high mount brake light,and ground is the shared ground for both circuits.I soldered them together and now everything works like it should.I guess over the course of 20 years they became brittle and being opened and shut finally cause the break.Hope this helps someone else out in the future.

 

Step 1 - Define problem

Step 2 - Troubleshoot

Step 3 - Solve problem

Haha, sorry you had to have a one way conversation with you, yourself and YOU! Glad to see you found what was wrong and fixed it

 

good job updating. hopefully it will help somebody in the future.