Hi,

I have a 1979 F350 4X4 400M. I am going to do the 3G alternator conversion. I do not have the green wire going to the external regulator. According to the schematics this wire is for a guage set in the console. This wire is also "hot on run". I also notice that this wire also has a resistor (510ohm). My question is can I run a "hot on run" wire from my ignition switch directly or do I need the resistor for a voltage drop? This wire would go to the "I" terminal on the alternator.

 

Your truck should have this wire, either on the "s" terminal of the regulator(gauge package) or on the "I" terminal of the regulator(idiot lights).

Be that as it may, what I would do is get a small light bulb at the parts store and install it in the dash. This socket must be plastic or the light bulb must have two wires, since it will not be grounded.

Run a wire from the key on power you were talking about, and run this over to one of the new light bulb wires. Take the other light bulb wire and hook to it, and continue out to the "I" terminal of the new alternator. The light will light when the key is on, but the engine is off. When the engine starts, and the alternator starts charging, the light will go out.

The resistor is not for voltage drop. It is wired around the light bulb. The resistor is there in case the light bulb burns out. If the light bulb burns out, the circuit will be broken, and the alternator will not charge. This is easy enough to catch if you know how it works, but if you install the resistor, the circuit will still be connected through the resistor, and the alternator will still charge.

 

Dave,

Thanks for the reply. My truck has the ammeter in the dash, I also installed a volt meter to tell my whats realy going on. If I take the wire off the "S" terminal and connect it to the "I" terminal of the alternator this would work?

 

Yes, that would work. It should be red/green or green/red.