Problem: when the lights are on, the L side brake light is always on, so the left side tail is much brighter than the right. When the headlights are off, things are normal. Any thoughts?
Car is a '95 Ford Aspire.
yep. If this is a two element bulb (some **57) ..the two elements join at the ground. They break off from the ground..but are joined to each other. When the parking light is hot, it grounds through the brake light filament. If you put on the brakes with the parking lights on, the right side would light up, and the left would go out (12v vs. 12v with no way to ground).
Had the same problem before and it was due to plugging in the wrong bulb for the socket, 1 terminal into a 2 terminal socket and the terminal was shorting the 2 together.
Replace the bulb and all is good.