1989 7.3 voltage regulator on a 1986 Harness. Will it work? What is the 4th terminal

[SkylabTech86IDI]

Hey all I have a 1989 F250 7.3idi voltage regulator and a 1986 harness F250 6.9idi

The voltage regulator has 4 male connectors on it and the 86 harness only has 3 female connectors - do I need an 86 specific voltage regulator or will this one work?

 

[franklin2]

It will work. Ford had two different ways they wired the regulator.

The 4th termiinal which is the "I" terminal is only used in a truck that has a "GEN" light in the dash. The 87 has this with a voltmeter in the dash also.

The other way is a truck with a ammeter. The 86 truck had a ammeter,, so the "I" terminal is not used and the alternator is wired a little different. This will be taken care of if you are using the complete 86 harness. The regulator is the same and the alternators can be the same also. A lot of the old early 80's f100s had idiot lights instead of gauges, and those would have used the "I" terminal also.

 

[SkylabTech86IDI]

Thanks for the response franklin2. On the voltage regulator harness, it looks like this secondary S wire should be grounded out to the firewall, is that right?

How does the wiring to the alternator look?

 

[franklin2]

In your case, the "s" wire to the regulator goes to the ignition switch. The "s" wire on the alternator is not used. Here is your 1986 wiring diagram.