hardpike

Just got my 1st vette. 1979 L82 4 speed with 58K. I noticed 1 issue that I can use some help with. The rear lights (brake, directional, reverse) work while the head light are off. But once the head lights are turned on, I have no power. I have checked the fuses, bulbs, and brake light switch, and these items were fine. Does anyone know if this was a common issue? and if there is a common cause and fix for this?

thanks

joewill

are you saying your brakes, directional and backup lights do not work when your headlights are pulled on?

silver 1

check the wires going into the light scocket. i had a broken clip which gave me a bad connection and my left turn singal would come on but wouldn't flash and was week 4 way flishers work. mine was the singal wire going into the left rear light scocket.

hardpike

are you saying your brakes, directional and backup lights do not work when your headlights are pulled on?

Yes, that is correct. They do not turn on when the head lights are on. But work when the head lights are off

myoriginal77

Bad headlight switch ? Bad ground to it ?
Those would be my first things to check.
Also, since you just got it I would go around the car and physically check all the exterior bulbs, not just that they work but pull them out and check they are the correct one.
A few years back a friend had bought a '76 and it had a weird electrical problem, when the lights were one some things like signal etc. would work intermittently.
Turns out in the rear instead of a dual contact bulb someone jammed in a single contact and that one contact connected the 2 contract strips shorting them out and giving a circuit when you didn't want one. New bulb solved the problem and we found 3 other odd bulbs also.
Hope that helps,
Frank

bj1k

I agree with myoriginal77. Any time you have a weird electrical problem, the first thing to check is for bad grounds. Grounds can cause all kinds of things that don't make sense. And I also would start by looking at the headlight switch.

Ryan Kitchen

Its possible that you need new bulbs. C3 headlights take like.. unreasonably insane amounts of power. It might be that because the headlights are on, the rear lights are just super super dim.
Which could also be a wiring issue

7T1vette

Bad ground connections somewhere in that system...probably on the headlights.