Top break light thinks its a tail light?
 

Hello there!
I have a 1999 Blazer LT with a very strange tail light issue.
Last week I noticed that if I turned on the lights, the top break light turned on and that both tail lights were off.
If I press the break pedal the top break light becomes sliiiightly more bright, but the bottom ones are dead.
When I remove the 20A fuse Park LP, from underneath the hood, the top break light turns off (and the tail lights remain off).
With this fuse removed the break lights work when I press the pedal, both the top and the bottom break lights turn on as intended.
All other lights, hazards, indicators, headlights etc work as they should....
Any ideas to what the issue may be?

Weird stuff like that is almost always caused by bad grounds. check all the grounds for the lights (starting at the tail lights) and make sure they're all clean and tight.

Alright. I have checked the ground connection for the rear running lights (the one in the right rear corner) and it looks fine. I have been looking in Haynes but can not really make out where the other connections related to the lights are located. Anybody knows where they might be?

Here ya go. Let us know if you need help debugging the problem.



George