Ronnie wilkins

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After quite a few attemps 0n mt 70 for same problem (three wire alternator)I traced it to the fuse box.There were 2 yellow wires that came down out of wiring harness below drivers side windshield post.One of these wires were disconnected.test the conecter on alt.one has power all the time and one has power with ignition switch on.Mine had no power with switch on.Anyway when i hooked this wire up to fuse box terminal that says ignition,checked connector again with
tester it now had power.Pluged it back up and works fine.Now my three wire alt. works great.Ithink this yellow wire goes to starter or maybe the ignition switch.Forget what the diagram said.Good luck
Ron

jpatrick636

Exactly where is the "positive battery lead" you are connecting to?

jpatrick636

UPDATE:

When replacing a 3 wire with a Powermster 1 wire, the ignition wire (brown factory wire) to the 2 post terminal will serve to excite the alternator to charge at idle. Even though the other post (regulator) does nothing on the Powermaster. It may be beneficial to install the Powermaster 1 wire as a three wire to take advantage of this feature and have the option of using a 3 wire alternator in an emergency.

I'm Batman

All that being said, I still want my idiot light. Gimme a real 3-wire.

neoh77

Lots of opinions here...good arguments for the 3 wire indeed! I too have a 77.

I have the summit branded 100 amp variety alternator.... I took both red wires from the 3 wire setup (they should connect downstream anyhow) and ditched the third wire. There is one 10g wire from the alternator to a distribution point on my fender well. This feeds my electric fan setup and the factory wiring. I've added no additional loads to the factory wiring. The only time I have an issue is if the car is not running and the ignition is on the ON position. This will backfeed from the car's system into the fan. Easily resolved with a diode to block the backfeed.

If I had to do it again.. I'd stick with a 3 wire high output alternator. Hook one additional 8 or 10 gauge wire to the alternator output to a distribution point for any add-on accessories like fans, fuel pump etc. Just don't add anything to the factory electrical system and make sure it's in good shape...that's my theory and I'm sticking with it.

-Matt

jpatrick636

I'm not really defending one or three wire, just trying to share information. The one wire (Powermaster) will run the idiot light if hooked up like a three wire or with the brown wire connected to the spade closest to the battery terminal.

shafrs3

If God intended alternators to have only one wire, they would have been made that way.

David Ey

Well, I am real confused now. I got a 100 amp chrome Powerwhatsit from Summit and connnected it three wire like the catalogue said I could. Sometimes the idiot light would be on and sometimes it wouldn't. The alt. would always show it was outputting. Thinking it was bad I sent it back ($58 so it would get there fast) last Friday. When I called Sum.... I told them to replace it with a 140 amp model....an extra 80-90 $ . Called Sum.... today and they say it is a three wire. Their cat. says It is easily converted to a one wire. Now I have no idea what I will be getting.