I have a 1989 D100 pickup that is having some light issues. When I turn on my right signal, the front right signal flashes quickly, both of the rear signal lights flash, and it makes my dash flicker slightly. When I turn on my left signal, only the front flashes. If I hit the brakes, it causes my dash to light up slightly and my front signals to light up slightly, and my brake lamps act normally. If I turn on my head lamps, it causes my headlamps to act normally, and it makes my brake lamps come on fully like I'm hitting the brakes.

I've seen folks talk about the flasher relays in other posts. I have not replaced them yet. Would those fix this issue, or do I have to go chase down shorts

 

Do you have a trailer light hook up? Check the wires to the trailer electrical connection first. Your problem sounds like a ground problem or a short on the trailer wiring. This is the easiest thing to check. Problems here can make you think your truck is haunted.

 

Actually, yes I do. I will double check that tomorrow. Thanks for the idea. I DIY most of the wrenching on my own cars, but never mess with electrical much. Thanks for giving me a place to start

 

I worked on a truck once where the trailer brakes would engage each time the left turn signal flashed. The trailer connection plug had steel screws that held the wires in place. Water had run down the wires due to poor insulation and the screws rusted and shorted the wires out from rust flowers. That's the sort of thing you just have to look for. When you find the problem, I'll bet it will be something simple.