[mr48chev]

The truck is probably rejecting those ugly lights not wanting to have it's friends make fun of it at the next cars and coffee. I'm sorry but on older rigs that is one of the biggest waste of good truck bucks to be part of a fad that detracts from the looks of the truck that I have ever seen. At least the visors were sold new by chevrolet to keep frost off the windshields in Minnesota.

The fix as usual with most electrical issues is making sure that your grounds are good and actually getting to ground to ground back to the battery. n from the turn light ground connection on the lights to a known good ground. First look in the instructions that came with the lights and check the wiring circuits and make sure which wire is the ground wire. You did ground that UP flasher to a good ground under the dash?

I found the instructions for the flasher and it is straight forward and simple. I found what I think the lights are but am probably wrong but the wiring on them relies on the ground wire for the headlight if that is the wiring you have. If that isn't it, first thing is to go to the light manufactures instructions and see what that says.

That wiring diagram for the headlight bulb it's self in the second image has me headed to look at a wiring diagram for a 7 inch seal beam just to make sure that I am seeing things right.