i have 99 gmc sierra 2500 work truck brake lights quit working all else works ,even 3rd brake light i have checked fuses,brake light switch, bulbs, circuit boards,all check ok anyone have ideas on what is wrong thanx.... mike

 

If everything checks out OK-

Then they should work ?

Check em' at night !

Red, *<(:{)-

 

I would check for voltage entering at the printed circuit board. Those boards are renowned for failing. Use a multi meter

 

If third brake light is working usually turn signal switch is bad. Sometimes if you play with the hazard button, on and off a few times, lights may start working for a while.