Third brake light

The third brake light and corner lights have not worked in some time there is no power to them but I have all power to tail lights gauge cluster? I can't find a problem. Any help?

 

Did you check the fuse? I'm not sure if they're on a separate fuse or not.

 

I checked all the fuses and they were all good.

 

I checked the plug at the third brake light assembly and there was no power there is there a relay or lose wore somewhere in the circuit

 

The brake light circuit is quite simple: Power delivered by "10A STOP" fuse. Straight connection from the fuse (at JB/1) via green/yellow wire to Stop Light switch (by the brake pedal). From there the green/white wire goes to JB/3 (behind the dash). From JB3 one wire goes to high mounted stop, the other goes to rear of the truck to left rear stop light. No relays. Just wires, plugs and switch.

The 10A STOP fuse is powered from the same source as horn and ECU so I suspect if horn is working the "upstream" power works.