Originally Posted by eyecando
I agree. It's almost definitely a problem with a ground connection.
While I agree the assessment, telling the OP where to start looking will be quite challenging.
If it were my rig, I'd start by pulling the switch and looking for appropriate colored wires and attempting to trace the wires back through the ceiling or wall to a common connecting place.
Easier said than done, most times the manufacturer give very little slack.. Verify which color is Negative and which is Positive in your rig.. I believe in mine the white is negative, but that may not be a standard.
Best of luck, loose grounds are not easy to isolate.