My 87 f-150 was in the body shop, and they had removed the box to paint the truck. I got the truck back today and the signal lights don't work, the green arrow on the dash just stays lit, the park lights work, but no signal lights. I checked the wiring, and it looks all connected. couldn't find a ground wire on the harnas, is it possiblely grounded threw the harnes up front some where? I remember my 77 had a ground wire behind the tail light lens. I took a coat hanger and rubbed it on the frame and to the box ,but didn't help. any clues? thanks

 

usually its the "flasher/relay" in fuse box. But since they had the box off, I would say the ground is okay, if your parking lights, brakes lights, and hazards work.
You might want to check they didn't crush "pinch" a wiring harness for towing if you have one.

 

I forgot to mention, when I first tried the signal lights the left side did nothing and the right side blinked ever so slowly, not sure if it flashed at the back or not, but either works now.I'll try a flasher. you think the box must be grounded good since the had the box of right?. If all else fails I'll have to take it back over to the body shop

 

Check your brake lights, do they both come on? Turn the hazards on and see if they flash in the rear. Usually if its a ground problem these are effected also.
Check the bulbs (front and back), sometimes they will cause the problem.
Also check condition of light sockets. Maybe they are getting bad connection.

yeah if it gets to be too much, I'd take back to them and have them fix it.

 

The clue that it would be a ground problem, is if it acts different when you have the headlights on, with either the turnsignals on or the brake lights on. If you have a bad ground, the power will run backwards up through the other circuit instead of going to ground like it should. It is also possible they took the lenses out to paint the bed, and got paint down in the bulb sockets, making a bad connection.