[joemustang]

I bought a 68 coupe with the stangest problem. The brake lights and turn signals work with the headlights off, but as soon as I turn the headlights on, the drivers side rear light goes out and the directionals don't work on either of them anymore? Why would they stop working once I power them up ??

Thanks

 

[Putt]

It sounds likely that
1. There is a very poor ground at the left rear tail light housing.
2. There are some wires crossed at the tail light wiring area.
Two possibilities, I would start with the ground first and check the wire condition at that time.

 

[joemustang]

When I turn the headlights on, the headlights work. But the turn signal indicators both come on. If it is not the ground by the tail light, could it be the headlight switch?

Thanks

 

[Putt]

You have a wiring issue I believe, the headlight switch does not control or power the turn signals at all. A thought--have you checked the bulbs in the rear?? It is possible someone put a single element bulb in place and it is shorting across the two terminals and causing some backfeed in the syatem.

 

[joemustang]

I will check, but I think the one that won't come on is a dual filament.