third brake light issue
 

Hey guys I'm new to this forum, but I'm having an issue with my light I just can't figure out. My third brake light glows when headlights are on and ignition is on. Now i think its a ground issue but can't seem to figure out where the back feeding is coming from. Anyone have any ideas or things I can try? It's really been driving me crazy.

I forgot to mention its a 2000 Chevrolet silverado extra. Cab

Has there been any work done on this truck recently? Anything at all that might affect the lights. Try pulling fuses 1 by 1 until the third brake light goes out. That will show which circuit is causing the back feeding.

Well not recently, but I didn't really notice it till I added l.e.d lights and I had an alarm system installed with auto start and it would work fine in the daytime(auto headlights didn't come on) but once it got dark it would start and then die so I started looking around and realized it would die when the third brake light would glow. So I unplugged it and checked the plug on the back with a voltmeter and noticed my ground wire had about 12-14 volts going to it which is causing a "glow" to the light, it lights up when I press the brake but stays glowing when I let off, not sure if thus has anything to do wth it but I've also noticed at night with headlights on my cruise control won't work right, if I hit the brakes it won't reactivate unless I turn my blinker light onand off then it works till the next time I hit the brakes... ill try the fuse pulling idea and see what I can find out. Any other ideas is greatly appreciated I've also replaced headlight and the brake pressure switch thinking those were causing it but no luck