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Discussion Starter · #1 ·
I'm having a bit of trouble with the stability of the voltage from my 95 amp 3G alternator. I've been working with my back street alternator guy for testing it, etc. and I need some clarification on a wiring issue as it does look to be that at fault. I am using an illuminated push button on the dash to start the car and the bulb inside the button is wired to be the charge (alt or gen) light - so that the switch goes out when the car starts.

The 3 pin connector that goes directly into the alternator has the standard yellow/white (A), a green/red (I) and a black/white (S) wires. When my ignition is on, (before start) I am currently switching both the A and I wires to 12 volts. My alternator guy says I have to switch the A wire otherwise I'll damage the rectifier. Not sure if he knows I'm also switching the I wire. When the A wire is permanently wired to the battery and only switching the I wire my alternator voltage is stable and correct.

I have seen diagrams where the A wire is permanently connected to the battery (no switching) and only the I wire is switched from the ignition. Is this OK?

Is it OK so long as one of them is switched? My wiring is such that the battery is permanently connected to the B (output terminal) of the alternator through a 100amp mega fuse.

Can somebody shed some light on this as I don't want the car to catch fire.

Many thanks.

Tim
 

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Your A wire either goes all the way to the B+ side of the solenoid or spliced into the BLK/ORG main charge wires and it should have its own fusible link in the line.

Your I wire is the charge light. It is usually switched at the ignition switch and has the dash light and a 500 ohm resistor in parallel with the light between the switch and the alt. You can still run it through the start button light-(really cool, probably borrow your idea).

Your S wire is the stator. It goes from the 3 lead plug to the stator connector, the single 1/8" spade connector.

You should only switch the I wire, the rest are always hot.
It's that simple.

This diagram shows all the alt wires.
 

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Discussion Starter · #3 ·
Thanks Tom. Much appreciated.

What size fuse should I use in the A wire to the 12v source?

I'm assuming in your diagram that the box '14ga link' is my 100 amp mega fuse.

Is that too large to protect the A wire and regulator?

Thanks again.

Tim
 

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From what I understand is it is not recommended to replace a link with a fuse. Depending on the amp rating, the fuse won't handle spikes in amperage as well and may blow before a fusible link will. It will usually take a solid ground short to blow a link. I don't think there is a problem using a fuse. Just use a fuse that is rated less than the gauge wire that it is protecting.
 

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I am still using the Ford Alternator, but also have a newer one with three wires - Red, Blue, and green ;all in a black circular Plug on this alternator.

Can you spell them out?
 

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Is this a test? Don't know what you mean by newer. The 3G is what comes on the 4.6L. But, I would only be guessing.
 

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I think it's a GM style alternator? I got it in a front end engine kit years ago, but never used it.
 

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