I have an 85 c20 with a strange blinker/flasher problem. It started with what I thought was a bulb problem. My left turn signal was on solid when I engaged it.
I changed the bulb and it still stayed solid. After playing with it for a while the right signal started with the same problem. Now neither right nor left signal worked. Both solid when used. Changed the turn signal/flasher module (Auto Zone) on the fuse box. Everything worked fine again till I turned the headlights on. When I turn on the headlights, the turn signal lights come on solid at all times until I use the blinkers and flashers. Blinkers work and flashers work. Why do the signal/flasher lights now stay solid on my dash when I turn my headlights on? They do blink outside and inside when I use them. Thinking I bought the wrong module from Atou Zone, I purchased an AC Delco (SF224) turn signal/flasher module from Rockauto.com. Same problem

Your front lights are not grounded.

Thanks
I'll check that out.