Got myself a new problem that I'm having trouble diagnosing.

When I turn on my headlights my passenger side tail light goes out. Turn the headlights off, and only the parking lights on, and it works fine.

Anyone have a clue on where I should start looking?

I've been dealing with a headlight switch issue (melted connector) for a few weeks now. I've got a new switch in there and it hasn't melted yet (I stopped using my fog lights for now until I can get a relay installed.) I would think that the headlight switch controls both tail lights on one contact, so I don't see why only the passenger side tail light is cutting out.