79 f350 4x4 460 auto. NSS? So what is this wire for? It is disconnected or snapped in 2, just hanging from the steering column. This is a tilt steering column, no cruise control. Also the reverse lights stay on when the ignition is on, could this wire be the cause? Is it for the PRND12 indicator? And the PRND21 on the column does not light up with when the lights are on, I thought there is a light in there?

 

IIRC, blue w/ red trace is illumination; red w/ blue trace is reverse lights. You can check the wiring diagrams here:
1973-1979 Ford Truck Wiring Diagrams & Schematics - FORDification.net

A broken wire wouldn't cause reverse lights to stay on, but to stay off. Sounds like something's shorted/jumpered somewhere. The dash illumination feed being disconnected could explain a lack of illumination though.

 

Sounds like the wire for the gear indicator light. If you have a test light check for 12 volts when headlights are on to confirm.

Hopefully the bulb socket is still in the column. It is sort of a friction fit and you can't get to it unless you have long skinny fingers so it is easy to pull on the wire and eventually break the wire.

My indicator light wire was broken at the socket. I could not find a replacement socket, so I found a universal light pigtail that used the same size bulb. I then disassembled it and put the guts inside the original column bulb socket and spliced the new wire into the ford harness.

 

Not sure how yours goes together, but in mine, the bulb is mounted to the turn signal switch - you have to pull the steering wheel to get to it. Upper right corner here: the black twist-socket just like the ones on the back of the instrument cluster.

 

78 and later columns are different than above. You have to remove the black plastic trim piece between dash and column at a minimum to access the light wire. My new turn signal switch did not include the illumination wire or socket. Had to remove it from the original switch.

 

Ah, good to know. Didn't realize they had changed that detail.

 

yes the wire was for illumination on this steering column, I put the test bulb on it and it comes on with the light switch