[Milwxman]

I have a '66 Pontiac Tempest and the tail lights work fine until I turn on my headlights. When I turn on my headlights they get bright like the brake is depressed and you can't see the brakes or turn signals.

When I hook to tester everything seems fine. Need help.

Milwxman

[mike nixon]

IT sounds to me like the brake and tail wiring is switched.

Mike

["QUICK-SILVER"]

Originally Posted by Milwxman

I have a '66 Pontiac Tempest and the tail lights work fine until I turn on my headlights. When I turn on my headlights they get bright like the brake is depressed and you can't see the brakes or turn signals.

Need a little better explanation of the problem. You said, "tail lights work fine until I turn on my headlights". Are you saying tail lights are ok with headlight knob pulled out to the first notch, then go bright when the headlight knobs pulled out all the way. OR are you telling us brake/turn work ok untill you pull out the headlight switch to first or second notch.

To most folks tail lights are just the red lights on the back of the car. When you're talking about lights and wiring on the back of the car, you're talking about two different wiring circuits. The dim side of the bulb is tail lights and the bright side of the bulb is stop/turn.

If it is just a matter of bright and dim being switched, it's what Mike said, the power wires are switched at the sockets. That happens alot when new sockets get installed.

If not.........we need more detals.

[Milwxman]

Thanks I will take a look at it today. I think that I might try switching the wires first to see if that works. If not I will post back with more details.
Thanks again.

[Peter Serio]

One other thing you might want to check: The way many low priced GM cars made prior to 1967 were wired, actually any Lemans or GTO built prior to 1967. They use just one lightbulb in the dash (it's the one with a lime green filter over it), to indicate when your turn signal(s) are flashing. The "+" feed back thru the wiring so that the bulb(s) that flash use a ground pathway back thru the dash wiring AND then all the way to the other side of the car; over to THE non-operational bulb filament on the side that's NOT flashing. If you have a bad ground on any of your sockets or a rusted front bumper, this could cause a problem. At this point if you've got a really chopped up wiring harness with sockets that have been cut and replaced, you may just want to order a new trunk wiring harness. (This applies mainly to 66 & 67 GTOs as they use 3 and 2 bulbs per side & you never can find a perfect harness, ~the cars are just too old. The weirdest thing I ever ran across was: years ago, a guy brought an old car into the dealership, whenver you pressed on the brakes ALL of the parking lights would glow, dimly. Turns out some idiot at a gas station the week before has forced an 1156 bulb into one of his rear taillamp sockets, (one that was suppose to take an 1157 bulb)! This cased the electricity to back feed into the parking lamp string. I guess the only reason I remember it after all these years was it was one of those typical electrical problems, that took 2 1/2 hours to find and less than 2 minutes to fix!