Scratching my head...
I have an '87 F150 302 long bed standard cab 4x4... A few weeks ago the front driver's side marker went out. I replaced both bulbs and then neither of them worked in the running light position. Then the dash lights went out and I replaced the dash rheostat switch - that fixed the dash lights but the interior left turn indicator light remains on when the headlights are on but not the right one. Still no running lights (corner markers in the front) the back running lights, brakes, hazards and turn signals all work. The front hazards and turn signals work - just not the front corner markers which are the same bulbs as the turn signals. I also changed the hazard relay for grins.
All other illumination works on the truck - interior lights, head lights hi/lo beams - reverse - license plate.
I don't know enough to figure it out - thought I'd try to ask the brain trust. ;-)
Thanks for the help in advance if anyone actually sees this... ???
Do the marker lights in the fenders work? If they do, that means you have power on the front part of the running light circuit.
If the fender lights work, then I suspect a problem in the light socket itself. One clue to that, the dash light being on when the headlights are on. That indicates a bad ground in the left turn/marker light. You replaced the bulb, so it's most likely a problem in the socket itself. I think you can get them at the store and splice them in.








