Short in the wiring or the lamp holder for the tail light is corroded.
Short in the wiring, or the circuit is overloaded.
no i did not replace head light switch
why does my turn signal light keep burning out and why is the sockets and plastic lens melted.
Short in the wiring or one of the bulb receptacles.
you could have a short between the two.
Somewhere between the fuse and the bulb
A short in the wiring.
short circuit on trailer light wiring
Dead short to ground in either: Parking light socket or wire to Tail light socket or wire to Dash panel lights Remove 1 bulb and/or socket at a time to try to determine which is bad
A short in the wiring (grounding out)
Short in the wiring or inside one of the plugs.