First time poster, so apologies if I'm not doing this right. My newly acquired '79 F100 has an electrical gremlin I'm trying to track down. I don't have a brake light at passenger rear lens. Driver's side functions properly. I have running light and turn signal, but no brake on passenger side. I've chased the wire all the way to the cab and have yet to find the issue(green wire per diagram). Figured I'd ask to see if anyone else has ran into this before I keep peeling back the layers. Any information is appreciated. Thanks.

 

Did you check the brake light switch that is on the brake pedal arm? If that is out of adjustment then you will not have brake lights. I had the same problem.

 

Brake light switch functions. I did have to adjust it as brake light would stay on. And my driver's side light works fine (running, brake, signal). I just don't have a brake light on passenger side.

 

Sounds like issue may be in the directional signal switch in column. Does it light when the 4 ways are on?

 

Negative on the 4-ways. All 3 other corners flash.

 

Have you checked whether you actually are getting voltage to the rear right? A test light would show you if you are getting juice when the brakes are depressed. Also check the ground through the socket, it is quite common for the socket to look good but have a poor or nonexistent ground. Sockets are cheap.

 

I had no voltage at the bulb with a test light. I checked at the plug underneath the bumper and could get a very faint response from the test light, but no where near what the driver's side produced. This led me to believe the issue was further upstream. I actually replaced the ground wires for the bulb at the housing. I didn't check the actual socket however, so I'll check there also.