I've found that it's usually a bad connection either in the bulb socket, the metal contacts in the light unit itself the socket screws into, or the main harness isn't engaging tightly enough in its plug.
I seem to recall having a short in my bumper marker light. I'd fix the fuse, and it would short out again. It may not be exactly your situation, but it did affect my tail lights as well since they share the same circuit in some weird Lucasian way. At least, that's my memory of it. Maybe check the wiring to your bulb there?Well…everything was fine until I turned the truck off. The second I turned off the ignition, the fuse blew again.
Yes, I’ve had an aftermarket pioneer for years but the connection behind the detachable face went bad so I replaced it a year or so ago. I don’t think I’ve had it inspected or legally on the road since. So the issue could have gone unnoticed until now….now that I’m trying to get it inspected!!aftermarket radio?