91_Thunderbird can anyone help me fix my signal lights

When you switch on the headlights do you have tail lights?

Ya but when I brake they don't light up

My best guess would be the turn signal switch. Especially if your third brake light is still working. Power from the brake light switch flows through the turn signal switch to the brake light bulbs. This way the brake lights will come on and they will flash when signaling a turn. Put your 4 way flashers on. Do the rear lights come on then? HTH. -Jim

Ya but just when I turn on my head lights

Only my the light from the spoiler turns on

Here comes a dumb question & I'm only asking because you didn't mention this in your original post. Did you check or replace the light bulbs? -Jim

I did and dare good....

OK cool. You'll need to get a wiring diagram to see what (color) wires are involved at the turn signal switch. Then check those wires for power when you step on the brake pedal. You may need a helper. You'll probably have power going to the switch but none coming out to feed the rear stop/turn bulbs. HTH. Keep us posted. Good luck! -Jim

Sounds like you may have a bad ground, and that is why the 4 ways work when your headlamps are on. Start where the harness grounds to the body and work backwards, running the wire, checking for chaffed or broken areas.