The PO hacked some wires on my 79 F250 4x4 and Im needing some help. Coming out of the C6 is 4 wires with a square plug: Red w/ blue stripe Blue w/ red stripe Black w/ brown stripe and white. The wires are just hanging under the truck and I cant figure out where they go. Could these be the wires for the tail lights and marker lights? That complete harness is missing and I will be replacing all of it. Next I have 2 purple wires that both have white or lt. gray stripes exiting from the driver side cowl that has a plug on the end and I think it goes to the brake proportioning valve? Is this correct? I have more but this will get me started. I have a few other trucks here but none of them are complete enough or hacked worse to trace the wires.

 

They are for the NSS & back-up lights.

They normally run up to the firewall and plug into a connector at the top of the firewall

 

which ones? 4 wire plug or 2 wire plug?

 

4 wire plug. I think mine plugged in just beyond halfway on the passenger side of the firewall on the top.

 

OK got that one last night. I cant seem to find the wires that power the tail lights and marker lights. I took the harness that runs from tail light to tail light and the short piece of wire that runs through the bed to connect the marker lights from another truck of mine. I just cant get from the rear bumper to the front of the cab. Any suggestions?

 

after the harness exits the cab just beside the brake booster,
It runs along the frame on the driver side.

When it reaches the back of the truck,it spilts ....One runs up to the left tail-light and the other runs across the back to the other side with a wire branching off out of the harness for the license plate lights.

 

Ive got the section that Ts off to the tail lights and license plate lights but cannot find them once they exit the firewall. What colors are these wires?

 

There should be a connector that comes off the main harness where the frame rail harness connects to.

You should have some of the following wires colors in the section you are looking for...

Brown: marker lamps

Green: RH turn signal and Stop

Yellow/Black: LH turn signal and stop

White/Purple: Backup lamp switch power feed.

Just to name a few wires ...


There is another connector where the frame rail harness connects to the rear harness. (Close to where the rear harness splits for each taillamp as mil1ion described earlier.)


On your first post you mention wires cut off of the NSS. They should be this color at the NSS or Backup lamp switch

White/Purple: Backup lamp switch or NSS power feed.

Black/Red: From the Backup lamp switch or NSS to the backup lamps

Red/Blue (Two wires): One goes to ignition switch, the other goes to starter solenoid from the NSS.

Since the colors do not match the above, can you double check the wire colors and/or can you get a part number off of the case of the transmission or NSS switch? It sounds like either the wires are faded, or someone may have swapped trannies with a earlier or later model. It could also be non standard wiring. Seen that happen too.


The Brake porportioning valve wire colors are Purple/white.

Hope this helps,