I located my new in box 70's F250 starter relay. I am going to use this relay on the drivers side fender, instead of the Dodge oem bosh style 30 amp relay, as per Bearkiller. Just to be sure - where would the 85,87,87a,86,30 wires go in relations to the Ford old style relay (with post a = positive, post b out to starter solenoid, small ignition post, and small S post = neutral).

 

broncobilly,

I am going to make a stab at walking you through wiring the Ford relay/solenoid.

It matters not which of the two bigger studs gets whichever of the two big wires that make the circuit from battery-HOT to starter-solenoid.

Route a heavy wire, 8-AWG or so, 6-AWG would even be better, from battery-HOT to either of the larger studs on the Ford relay.

Route a second wire of the same size from the other large relay stud down to the starter-solenoid; connect this wire where the factory BROWN wire currently resides, the one that is taped alongside the BIG battery-cable.

Leave the factory BROWN wire dis-connected.

Now we need a START signal to activate the FORD relay.

There are two ways to accomplish this, actually three if you count the option of adding a push-button START.

Method one is to route the BROWN wire, that you dis-connected from the starter, to the little "S" (or is it "I", I can never remember) terminal on the FORD relay, leaving the DODGE relay and all of it's wiring intact; if the FORD relay is GROUNDed, turning the key to START should activate the FORD relay and thus start the engine.

I always bench-test the FORD relays to ascertain just whichever of the two little terminals is the correct one to use; not all FORD relays will have two little terminals, many have just one, making the right choice obvious.

The second method is to ascertain whichever wire activates the DODGE starter-relay and clip it loose UPSTREAM of the DODGE relay; route this wire to the START terminal of the FORD relay.

If, like myself, you prefer a push-button, then the "cold" wire from the push-button connects to the START terminal.


I hope I haven't confused you too much.

 

Bearkiller,
Much obliged for that great info!! Even an electrical neo-fite like myself can follow your precise directions : ) I really appreciate the help, and hope to wire up the Ford solenoid this coming weekend!