The fuses are intact. I don't 4 wheel, didn't high center anything. What can cause just the rear running lights to not work? while all other functions work. The headlights work, the front drive lights work. High beams work. 1988 F150, ext cab, 5.0, automatic transmission, 2 wheel drive.

 

The dash switch can do this. May be on its way out on you. I had a 95 PSD that if I was slow with the switch I could get them all to work but in the end it did what you are describing. I never fixed it. It got a tail light warranty out of town on a flat bed to its new home.

 

Loose connections (power/ground)
Are the bulbs any good?
MLPS?

 

Check the wiring in the rear. It's extremely common for the wires to corrode and break regardless of your driving habits. If you or someone spliced in a trailer connector, check there first! Being the tail lights, it could have broke in the harness before going into the first bulb (driver side)

 

Thanks guys. It wasn't the switch. I tracked down the wires...took off the trailer harness, saw a snapped wire under the frame. Now the lights work. There must have been something that fell out of the bed between tailgate that fell into the wire. I did take off light covers and removed the 'hacked' wire that was spliced into both left and right lights. Horrible wiring job.