Left rear taililight running light comes on with headlights, but Brake Light does not

[edpdx]

Fellow driver indicated that my Driver rear Brake light was not working. It has been intermittant the last few months. Someone brings the condition up, I look, and it is fine?!?!

I replaced the socket today, but same deal. When I check for continuity from the supply wire (on the new connector) to the contacts, all is fine.

Bulbs changed with known good ones. Other brake light works fine. How could this be?

 

[cucvrus]

Sounds like a grounding issue. When ever anything strange happens with lights I always check out the grounds. It could be pulling ground thru a positive feed wire that is not energized. I know what I mean but am having trouble documenting it. Check your ground with a test light hooked to positive and probe the ground terminal.

 

[TGP (IL)]

Could be the Ground as cucvrus stated. Also a bad feed wire or connection.
Last, could also be a worn turn signal switch.
Does it flash with the switch?
Get a test light and trace the circuit.
Tom

 

[MarcusOReallyus]

Sounds like a grounding issue. When ever anything strange happens with lights I always check out the grounds.

Yes, yes, yes, and yes again.

When electrical gets weird, check grounds. And, as Good Sir Richard says, use a test light, not a meter. You need a load on the circuit. Meters put negligible load on a circuit.