Originally posted by Baldy:
Not true, Bill.
With a bad ground to the taillight assembly the current from brake light filament can't find ground there, so it goes from the ground side of the brake light filament to the ground side of the taillight filament, through that filament to the taillight wire, back to the switch and out to the panel lights where it finds ground. This is a very common problem on old vehicles (and new European vehicles including Mercedes). This is the same problem when you see someone in front of you putting on their brakes and a taillight goes out. In that case there is a high resistance ground that can't carry the higher current of the brake light. The brake light and the taillight are lower resistance than the the dash lights, that's why they come on.
Pablos49, the old light switch won't have anything to do with the problem.
It has happened to me more than once. The bulb being bad also will do this stuff.
