i have a 1986 iroc. The third brake light comes on with my rear defogger when i touch the brake. The 3rd light and the defroster stay on when brake is released. To turn off light i must turn off the defrost switch. Everything used to work right until my defroster quit about three months ago. The ony thing done in that 3 month span was today. I noticed my 3rd light was out and checked the bulbs. They were all good. When I put it together, the brake light works as mentioned above instead of releasing the brake and the light going out. HELP?????????

 

Sounds like it could be a bad ground connection. Check the connectors on each end of the hatch lift strut on the passenger side.

 

That is truly bizarre! The defroster wires are the ones that go through the hatch stuts but the 3rd brakelight, at least on my Camaro, are controlled through the contact switches on the rear hatch opening trim. I can't imagine how the 2 could get crossed!

 

Yup. That'll be it. I had the same problem on my 86 TA. Turns out it was a bad connection at the bottom of the passenger side strut. A few inches of electrical tape was all it needed

 

On the 86 at least, with the 'humpback' third brake light, both that light and the defroster share the same ground connection through the passenger side strut.