Having a problem with my '88 4 Runner driver side brake light. When the headlights are off it works fine. When the headlights are on it doesn't work at all. When I first noticed the problem I removed the lens and replaced the bulb, it was burned inside the bulb glass was all grayish black. Replaced the bulb and everything worked fine for about a week. Then checked it again and it was burnt again same color on the bulb. Then I replaced the bulb with a long life bulb. It works with the lights off but not with them on, bulb not burnt this time. The wiring looks good but I'm not very good with electrical stuff. Also my license plate lights don't work, after replacing the bulbs that weren't burnt. The truck has a tow package on it but it doesn't look like factory wiring on the plug harness. I have no other issues with electrical problems on this truck. Just hoping someone could give me some advice and if it's a short how to I go about tracking it down? THANKS!

 

If your not using the trailer harness, I'd say remove it to eliminate that as the cause of your prob.