Classic symptom of a bad ground. There's two signal bulbs on each side on the rear. With a bad ground in one socket, current goes through one filament, (can't get to ground), goes through the tail light filament, over to the other bulb's tail light filament, to ground in that socket. When you turn on the head lights, (just the running lights), the turn signal with the bad ground has 12 volts on both sides of the filament so it goes off.
You should also see the two signal lights on that side blinking alternately when there's a bad ground.
Sunday, March 29th, 2009 AT 10:06 PM