Brake light problem on JGC

The left rear brake light on a friends Grand Cherokee is acting up. When the lights are off, it works normally. But if the parking or headlights are on, the brake light is not on at all or only very dimly.

We have checked and replaced the bulb, and cleaned the contacts, to no avail. We have even replaced the passenger side bulb just to be sure.

Anyone have any thoughts?

I did a google search and this question has been asked MANY times, but never an answer. Did any of you ever get this problem fixed?

I concur.

When the running lights are off, the brake light filiment is getting a ground through the running light circuit, when the lights are on, the ground source isn't there and the brake light does not come on.

I know someone with the same problem. where is this ground? If I remember correctly, the housing is held in by two screws, but they run through a plastic tab on the light fixture, no metal.

Charles

I don't know the exact structure of the lamps, but the description of the problem is classic loss of ground.

Or the contacts inside the housing ... (this is the most common area for this problem)

Another thing is that the bulb itself has an open filament. This is even more common than the socket problems in the housing. I know you said you replaced the bulb, but did you install another bulb with the same problem? I would be taking a known good bulb from the right side and plugging it into the left side. (I would really be getting my volt meter out and testing the bulb and socket, but barring owning a volt meter, the switch-test is the next best thing.) If the problem follows the bulbs, then you have a defective bulb, or handful of defective bulbs. If the good bulb no longer works in the bad socket, then mysteriously works again in the good socket, then you have a socket related problem.

bad/rusty 6pin connector to the tail lamps.