Passenger brake light not working

[RustyPile]

Originally Posted by PbFut

If the front turn signal works correctly, then doesn't that indicate the switch is ok? Rusty, you know these trucks well. Is there some funky stuff with the switch and blinker that would allow one end to work and not the other? Do the easy stuff first. Swap bulbs to verify if its the bulb and or socket or not. Then very the socket is not corroded. Then verify if you have power at the socket. Then note color of wire. Go to firewall and unplug the connector on the 4 wire ribbon cable. Note the color of the wire matching the turn signal wire at the socket and test the pin for power on the firewall or jump 12v to the pin on the cable and see if the bulb lights.

Re-read my post.. The brake lights and rear turn signals share the same wires from the switch, the same bulbs, bulb sockets, and also the same ground paths.. Because of this "sharing", if the turn signals work as they should, then the problem with brake lights is NOT any of these items.. The problem is before the signal gets to the wires.. That's why I suggested testing at the plug.. I know the results of the test, there will be no voltage there.. I just wanted to "steer" the OP away from fiddling with all that other stuff and possibly creating another problem..

The front turn signals AND the dash turn indicators get their signal from the turn signal switch, but it is a totally different and independent section of the switch. To answer your question, No, that doesn't indicate the switch is functioning properly. It only indicates that section of the switch is functioning.

I realize wiring diagrams are very difficult for some people to read. But this is all laid out in the wiring diagram...