1972 4dr Maverick tail light problem

I have a problem with my right hand side tail light turn signal, brake light,back up light. When i turn the headlights it turns on but the turn signal wont and the brake lights. Thanks for your help in advance.

 

Try changing the bulbs.

 

The lights work. just the brake and turn signal don't work. I know the bulbs are good because when i turn on the headlights at night the light is on.

 

the bulbs have 2 filaments 1 for tail lights and one for stop and turn. One can burn out and the other will still work.

 

Thanks for all your help got it working it was a bad ground.