I have a question regarding the ignition switch on my 71 F250.

According ot the ford manual, the ignition switch has a Start-And-Prove-Out position and it also has a Proof terminal on back.

Question - what is the Proof terminal used for? Is this for lamp testing?

The reason I ask is that the offical ford shop manuals for (published by Ford) do not have a wiring schematic for my truck. I have leafed through the entire set of manuals and can't find a schematic diagram. Sigh.

-David

 

I seem to remember it is for testing the "brake" light on start, purple/white striped wire. It puts a ground on the light so you can see that the bulb works. I think it is so the light is worn out from testing it on every turn of the key.......so more can be sold LOLOLOLOL