why dont my turn signals work when i turn on my headlights on 1967 thunderbird

Start by checking and cleaning all the grounds in the rear for the lights, also check the lamp sockets, you may have to get some emery cloth and do some polishing on all the contact areas an ground wire locations.

Do you have taillights and brake lights with the headlights on? If so, power can get back there. If I remember correctly these cars had a complex system for the sequential rear turn signals in the rear. I believe a rolling drum type of gizmo was activated to accomplish the sequential effect. Your best bet is to get a factory shop manual for diagnosis. Faxon Auto Literature in Riverside, California will probably have a reprint at a reasonable cost. They have a website. On a side note, your front parking lights are supposed to switch off when you switch on the headlights! If they are staying on, someone may have fooled around with the wiring. 1967 was the last year for that parking light set up and now, years later, it can cause confusion. Especially with law enforcement and at the inspection station! So I'd make sure that's working correctly and then tackle the turn signals. If your parking lights are hooked up wrong it may cause other issues on that same headlight circuit. HTH. -Jim

thanks guys,i have power back there I have the shop manual also I tried everything grounds cleaned sockets work cleaned brake lights work backup lights work sequential turn signals work left and right but as soon as I turn on headlights turn signals don't work I guess is to take out head light switch and check it love electrical !!!!!!!!!!!!!!!

The only thing the tail lights and the brake/ turn signals share is the grounds, have you ohmed out the grounds wiring? that old it is possible you have some internally broken wiring. Also check for cross circuited lamps, I've seen all kinds of different electrical problems cause by a single lamp filament breaking off and welding itself to the other one. I think your headed in the wrong direction with the headlight switch.

You're welcome, glad to help! Thanks for the update! Do the rear turn signals flash with the hazard warning flasher (4 ways) switch and headlight switch both on? I agree with tennisshoes, since the taillights work I don't think it's a problem with the headlight switch either. Turn signal switch, possibly. It's plastic and can break. That switch completes the circuit to ground to activate the turn signals. HTH. -Jim

yea I think I will try the turn signal switch keep you posted.......

I could be wrong but it just doesn't sound like a turn signal switch cause it all works as long as the headlights are off.