I have been away from FTE for awhile, some of the categories have changed, admin, please move this if it fits better somewhere else for the OBS.

Truck: 1997 F350 4wd
Problem: Rear brake lights only work sometimes (saying "rear" to mean the brake lights on the back of the flatbed and the headache rack) because the brake light on the cab always works), been going on for about 2 years for has gotten worse lately - (worse meaning they don't work more often than they do work.
- flashers work
- turn signals work
- 3rd brake light on the cab ALWAYS works
- when the rear brake lights DO WORK, the from left turn signal also illuminates - that's how I know when they are working and when they aren't - meaning, if I press the brake pedal and I see the green arrow light up for the left turn signal, then the rear brake lights are working
- cruise control works
- O/D functions correctly

I am wondering if the brake light current somehow travels though the turn signal switch and something is not functioning correctly - puzzles me why the front left turn signal also lights up when the brake lights work.

Any suggestions? I appreciate the help. Thanks

 

 

I had a similar problem several years ago with my 78 F-150. I eventually found a bulb, front turn I think, where one of the filaments had burned out and wrapped itself around the other filament. This caused current to go other places than intended.