I am looking for a wiring diagram for under the dash. I have a 77 f250 custom and I am putting in a classic car radio, old look modern technology. I removed the existing after market radio that was from the 80s and the wires were not connected.. when I bought the truck the radio had sporadic power as I drove it from Idaho to Alaska. I do not see any wires that are broken from the dash wiring harness but I am not sure which wires are supposed to be for the radio and the Chiltons book I have does not show any specific radio wires. anyone have a diagram? I am fairly certain I am going to have to cut the factory wiring connectors off to splice this new radio in, even though it still connects with 4 wires. any help is appreciate. thanks

 

Look for a green plastic plug with two wires, one blue w/red trace, thats for the radio lighting and one yellow/ black trace wire, that one is radio power.
Also, go here for the diagram. They don't have the '77 yet, but for this you can use the'76 diagrams. On the '76 diagram, the radio wiring is on page 3, location C-14. Basically, it's in the upper right hand corner of the diagram.
http://fordification.net/tech/wiring.htm

 

thanks! you wouldn't happen to have pictures of the harness would ya? I think i have the right two wire pairs but i would basically kick myself if i cut the wrong wires... any way to tell they are infact those wires? i have heard back then it depended on who was putting the truck together if they followed the wire color codes...

 

Have you looked in here? I would suggest opening this thread on a lap top or a home computer. Might blow up a phone. lol LOTS of pics and diagrams.https://www.ford-trucks.com/forums/1...then-some.html

 

Here's one from another post that's had the wires a little butchered, ignore the red arrows.
As far as color codes, sometimes the diagrams don't match reality but feel confident following them. A lot of the plugs on these trucks only go on one way.

EDIT: Here's a quick lesson on Ford schematics.
Look at the diagram, the green plug is listed as connection C-506. The diagrams will tell you everything you need to know. Look towards the bottom of the page, see the plug drawings? Go to the picture labeled C-506, this is a drawing of what the plug looks like, it also tells you the color of the plug (green), the color of the wires and the location of the plug. Everything you need to identify the correct plug.
On this particular plug you'll also see the schematic has an error in the color codes. In the schematic, the plug is listed as having a blue/red wire and a black/green wire, this is incorrect. The drawing of the plug however, has it right yellow/black and blue/red.