my son saved up and bought a 89 f150 351w c6 4wd std cab short bed truck with 77000 orginal miles. the truck has been sitting for 12 years. so 2 fuel pumps and 8 injectors later it runs. the issue we have is the left brake light stays on all the time and the right will not light up for park or turn. checked with a test light so i know the bulb is good also plugged in a new t/s switch and unplugged the stop lamp switch. Any ideas?

 

Check to make sure you have the right bulbs. Also might want to pry the tabs on the new bulbs out just a bit. I had a problem with a new bulb that I put in mine, they didn't light up at all. I pried the tabs out just a bit and it is working now.

 

also i'd trace the wires as far back as you can starting from the tail lights and make sure there arent any bare or broken spots. i had a similar issue with a 88 ramcharger i had and it was a rotted out wire in the fender well about 2 feet from the light itself. the one wire messed up both my tail lights and side markers.

 

update

found a broke wire so now i have 2 tail lights but the brake lights stay on all the time. i have power to both wires at the brake light switch just need to find where its back feeding from

 

looks like it might be the speed amplifer just need to find it and test it

 

I'm assuming you have the connector off of the switch when testing for power to both wires. It could be the switch is stuck in the on position.

 

yes it was unplugged. while testing i noticed the wires getting hot. cut the tape off and the 2 wires were melted togther.
summary someone did a poor job of wiring a trailer and put a 30 amp not a 15 amp fues and melted the wires. so im tracing to find good wire to splice into and i think it will be fixed.

 

after about a foot a melted wire my brake lights are fixed