[jrmunn]

I didn't look back in the thread to see what lights are involved, but I can tell you how I fixed my intermittently working signal lights.

The rear lights were poorly grounded because of rust on the screws and in the screw holes that connect the lights assembly to the body (this also affected stop and tail lights), which also provides the ground connection. The front turn signal light sockets needed to be removed and the metal parts cleaned to make good contact. I also used some sandpaper in the hole where the socket fits into the hood. And the metal bulb holder needs to be fully inserted. All lights are now working.

Before doing the above, I had already put in wires between the body and frame to ensure a good ground connection.

These trucks were built tough to handle loads, and the electrical system is not complicated. But electrical components and connections seem to be a weakness, with rust being a major problem.

JRMunn