Im trying to get all the lights on our shop truck working. Right now everything is working except for the right rear brake and turn signal. No mater what I do I cant seem to figure out why they arent getting power. The truck is a 73 F250, I have a 76 wiring schematic that I have followed out and everything looks fine. I have spent more then a few hours comparing and testing and nothing seems to turn them on.
The left rear has a very simple layout, the wires go straight to the back from under the dash. The right rear is a different story, it goes to the front right turn signal them goes through all the front lights before leaving the front left. I could be wrong though, im tired and havent looked at the schematics since yesterday. I just remember it wasnt very straight forward.
Anyone know how the wiring on these trucks work?

 

Although mine is a 77, hopefully its still the same. I had a similar problem with my truck that your are describing. It turned out to be a faulty turn signal switch in the column. I took a wiring schematic and a multimeter, pulled the steering wheel off, and tested at each of the contacts. What I found was, at times, with the blinker stalk in a certain position, one side brake light and blinker were inoperable. It was intermittent and hard to find. But thats what it was. Turn signal switch. Good luck

 

pull the plug near the firewall that feeds the wires going down the frame to the tail lights. Do you have a blinker there? should be either orange or light green I think??

 

The plug near the firewall has 4 wires going to the back. Brown, yellow-black, green, and black-red. The yellow-black is getting the left turn signal but im not getting anything for the right.
Behind the front right turn signal there is a plug with three wires. Black, brown and white-blue. Front the schematic it looks like the brown should go back to the headlight switch and the to the plug by the firewall. I wasnt getting power from the brown wire at the plug by the front right so im guessing the turn signal in the front isnt returning power down the brown wire. I ran a temp wire from the white-blue to the brown wire by the headlight switch and got the back turn signals working.
That still doesnt fix the brakes on the right side. Any thoughts?

 

1973/77 F100/350's use the same turn signal switches (TSS):

D3TZ-13341-A .. TSS / M/T w/o Speed Control / Ford just obsoleted it, but dozens are still available from dealers/obsolete parts vendors.

D3TZ-13341-B .. TSS / A/T w/o Speed Control / Available from Ford: MSRP: $69.98 // FTE sponsor PARTSGUYED.COM price: $50.39

D5TZ-13341-B .. TSS / 1975/77 with Speed Control only / Obsolete / AFAIK, only available from Green Sales in OH and Porterville Ford in Porterville CA

 

Might could just pull the wheel and check that turn signal switch Justin mentioned. When I first got my 73 I had no brake lights at all. After checking everything I could, I was blown away when my brother in law traced it to one little contact in that switch. He temporarily fixed it but later I put in a new switch.

 

I'm with them. Turn Signal switch