You may remember my ordeal with my C-300's wiring. It was BAD. I re-wired it completely and have had no problems at all... until yesterday. I was checking the turn signals before setting out for a drive. The left one was fine, but the right seemed a bit bright. I got out of the car and walked to the front. You can not know how I felt when I saw the headlights flashing with the turn signal. My heart sank. I had installed my newly converted-to-12v Neg Ground AM radio, and had some of the dash out. It must be the switch. After checking EVERYTHING, I was really bummed. Looking for other things to check, I pulled the right rear socket. The problem went away! It seems the bulb was not seated properly, and the double bases were feeding e-lectricity from the flasher/brake circuit into the lighting circuit. I never would have guessed that this could cause the problem. All's well now.