The right turn signal on my 2004 Silverado 2500HD has a mind of it’s own. Sometime is works fine, sometime it turns on the flashers. Replacing the switch did not fix the problem. Left turn signal works perfectly. Any ideas? Thanks!
Bulb problems sometimes begin with moisture penetrating the bulb housing or socket and creating a bad ground.
Have you replaced both bulbs on the right side?
I have found in the past that some aftermarket bulbs won’t work in GM vehicles for very long.
One suspect is a bulb on the right side. The filament for the turning signal may be sagging and making contact with the tail light or parking light filament. This would then send power to all the lights. I would replace the turning signal bulbs on the right side of the truck and see if the problem goes away.