It’s a 1999 Honda Civic EX with the OEM spoiler, and the third brake light oddly turns off then stays like that for days or weeks or months. In some situations it’ll turn back on for days or week or months, the cycle repeats. It’s not a blown fuse, the bulbs are not burnt, could it be a simple loose wire?

 

My guess is it could be a broken wire. Get out a meter or test light and trace the wiring. Since the harness has to move with the trunk, the area where it bends would be a place to focus on. I would also look to see if the harness was cut/scraped/pinched by someone jamming something into the trunk.

 

Broken wire as in it could have been cut? I'll look for all of these when I get home. I'm also kind of clueless on where the spoiler wires are, it seems that it's hiding inside the trunk very well. The trunk weatherstripping isn't straight, so that's a possibility this guy put a lot of heavy stuff.

 

Not sure on a 6th gen. On my 5th gen coupe, the wires run along the side of the hinge arm from the trunk lid back to the wiring harness along the top of the trunk, right behind the back seat.

 

There shouldn’t be a harness for the oem spoiler, only a red and black wire. On the trunk hinge there are two tubings that cover the wires, it’s black plastic, you should know what I’m talking about, like heat resistant or something. One was actually for the third brake light so I followed that tube from the inside of the trunk, onto the trunk hinge, into the factory brake light behind the rear windshield at the bottom. It was one of those wires that connected to the chassis. Nothing was loose although I’m not sure because inside the trunk where the spoiler wire meets the tube, it’s in a very tight spot so pulling it would just make it more loose.

 

Maybe to fix this I would have to take the spoiler off but I don’t really wanna do that. The spoiler’s wire exits from the left underside of the spoiler going in the top left area of the trunk and it’s a very tight area.