3G alternator wiring problem

[Carb'dCobra]

Well I couldn't stop putsin' around with the wiring and I screwed up again. So I'm just going to go back from the start.

I have a brand new (not reman'd) 1995 5.0 Cobra OEM replacement 3G. How do I wire it up. Bare in mind, I have nothing left of the original harness. Everything is wiried myself (fuel pump, lights, etc.).

Correct me if I'm wrong but here's my current setup. My yellow/white-stripe wire runs to the back of the post on the alternator. I have a large 4ga wire running from the rear post to the battery. The white/black-stripe wire runs to the stator blade recessed in the case. And the green/red-stripe wire runs to my master switch in the cockpit, which I belive ignites the alternator when turned on. I also have a 2" pulley on it. Is that an overdriven pulley?

Now, the alternator has started making that horrifying screaming noise from the case when I rev up, and the case gets hot after about a two minutes running. I also appx. 16-16.5 idling volts @ 850-1000rpm (my rpm fluctuates) and 18+ above 2500rpm.

Help please. Jrichter I believe this might be your field lol.

 

[Mustang78]

remove the battery cable and see if it keeps running, the only time i've heard a high pitched squeal from an alt. is when i ran it without a battery for about 6 blocks..it puts a large amount of stress on the alternator, make sure its storing the voltage somewhere, if that's ok it might be defective, like a bad bearing or somethin..good luck i plan on doing a 3G real soon, how many amp is yours?

~Mark~

 

[HISSIN50]

I would not remove the battery cable with the car running. This could wipe out electronics and computer controlled items in short order.

 

[jrichker]

The green/red wire needs a 500 ohm resistor wired in parallel with a 12 volt dash light to
provide a proper regulator wake up circuit.

The following diagram provides the basic plan for alternator wiring. The 3G altenator would
use a 4 gauge fused power feed in place of the two 10 gauge black/orange wires.
You should also have a 4 gauge block to chassis ground wire.

Diagram courtesy of Tmoss & Stang&2birds

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/

http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

The 3G has a 130 amp capacity, so you wire the power side
with 4 gauge wire. It stands to reason that the ground side
handles just a much current, so it needs to be 4 gauge too.

Picture courtesy timewarped1972 View attachment 429930

 

[Carb'dCobra]

Do you mean I should ground the alernator? I have a 4ga ground wire coming off the back of the motor to the stock location as shown in the photo, and the front engine ground is 4ga and goes to the (-) battery terminal.

Anyway, I went down to advance and got the old alt tested. Turns out, a while back I must've fried the internal regulator and never found out until I had wired correctly. The guys over at Blue Oval Corral helped me in wiring it, since I don't have any OEM wiring in the car AT ALL. So I got a new one under warranty, made sure the wiring is correct, and it now puts out about 14 at idle (670rpm) and 14.5-14.8 around 300rpm (due to overdrive pulley I put on). Thanks for your concern guys.

 

[jrichker]

The ground you have now should be fine. No more grounds are needed in your case.

 

[HISSIN50]

The green/red wire needs a 500 ohm resistor wired in parallel with a 12 volt dash light to
provide a proper regulator wake up circuit.

Quoted for reiteration of importance. Just a straight run of wire (with no resistor/filament) will cause some real issue with a short to ground, of sorts.

Good luck.