Brake lights wont work when head lights are turn on

You have a bad ground.Look around the headlights first for broken, corroded or loose grounds.Then check at the back of the truck for the same.

Try just turning on the parking lights. Do they work that way? Do your emergency flashers work. This is a different circuit. Check fuses. Brake lights work with lights off? It may be in your switch connection. Corrosion, lose or shorted out wire, or as stated from uff4X4, corrosion on a ground somewhere. Electrical problems that sometimes works and some times don't are a nightmare to trouble shoot.

the rear lights work when the lights arent on but even turning on the parking light turns them all off. im not sure about the flashers.

It may be in your switch. If they work when the lights are off, the ground wiring is not an issue. The common connector between the front and rear lights is at the light switch. Believe it or not, the switch has been known to go bad on occasion. I hope it fixes your problem. Now if there is another connector between the routing sequence, I'm not aware of it. If it is, check if there is a fuse in the routing.

Yes it is pulling the ground from the park lights to burn the headlights.

it was a ground thanks!

Exact same problem on my 1500! What ground was it?

Im having this same problem could you tell me what ground it was

Our brake lights dont work when head lights are on. But they do when the parking lights and flashers are on.

Anna, look at the answers above. Since it is electrical, and on a "DC (direct current) circuit, you have a wire carrying the electricity to the lights, and to complete the circuit, it needs a ground wire making connection to the metal part of the car or vehicle to complete the circuit. If there is not a proper ground at the spot the lights are burning, it must travel further up the line to work. That puts a draw on the circuit and it may either not work the lights or burn out a fuse. Check the ground wires on the bulb sockets, make sure the wire is clean at the connections, and not broken. This is difficult if you are not well versed in electrical circuits. There are inexpensive equipment to test the circuits, but it take training to use it. Visual and touchy feeliy is the best starting place. The lights that go out when other lights are turned on is a good place to start.

I have 96 Tahoe and when I hit my brakes it blows the stop hazard fuse but when my lights are off the brake lights work Normal