My dad bought a 1988 1500. At first the right reverse light was always on and the blinker was screwed up. We replaced the bulb boards and checked the fuses. Nothing has changed.

What could be causing the issue? What else should I check for?

Thanks

 

I would crawl under the truck and trace out the wiring. I would guess somebody may have spliced in a trailer wiring harness. and now it is becoming corroded and eroding

 

If is an auto then it makes no sense...the reverse light is on the neutral lockout switch but on a stick the neutral lockout is on the clutch and the backup light, I suppose, is on the tranny itself or the shifter. Also, I have seen Chevy put the backup light switch in the steering column locking mechanism. Sometimes people disconnect the links that make it operate and turn the ring on the steering column counter-clockways so you can remove the key and leave it there, not realizing that activates the backup lights. Find the backup light switch.

Here is what I am thinking: Turn signals, Brake lights, and tail lights can have shared problems but the only time a backup light has a shared problem it is usually a ground issue. I'm betting on the switch.