When I turn on my headlights my turn signal and brake lights wont work, also my right turn signal light stays on, on the dash, when I turn the lights on My truck is a 78 F-100

 

Take all the bulbs out, front and rear, and scrape and clean the brass part of the bulbs and the little tang that contacts the bulb. If that doesn't work, then replace the sockets. If your left turnsignal stays on with the headlights, the work on or replace the left front turn/marker socket. If the right one lights, then work on the right front.

If both brake lights will not work with the headlights on, then work on both rear sockets.

 

I would just replace all the bulbs and clean the sockets really good like Dave said above. While your at that check all ground wires and all other connections.

 

Turns out that is was the light socket on the right front. It had a good ground wire going into the socket. but the ground rod inside the socket was rusted in half. It cost 10.00 dollars to replace the socket from O'reillys. Now it all works fine. Thanks

 

Franklin2: Just wanted to comment on your posts. Been on here almost a year now and your answers are always precise and easy to understand. Something that is hard to pull off. Even when I know what I'm talking about, it's hard for me to get the message across typing.