Alternator Getting Hot Hot! What is the deal??

3G Alternator Getting Hot Hot! What is the deal??

Hi all,

I need an alternator guru that can give me some clues as to what the heck is causing my 3G Alternator to get piping hot after less than a minute of idling.

Background:

1. I have a 65 Mustang Coupe. I put an 87 5.0 EFI motor in it and went with a 3G alternator setup. Alternator is brand new.
2. Motor is just basic Crank, Water Pump, Tensioner, and Alternator on my serpentine belt. Super basic.
3. With the belt off the alternator spins very smooth.
4. Alternator charging cable goes to a 175 amp mega fuse, then to the starter solenoid where it shares a mounting bolt with the positive battery cable.
5. Alternator seems to be grounded just fine.
6. I've checked and rechecked my wiring schematic and I think I'm fine. The schematic I'm using can be found at:
http://fordfuelinjection.com/public/alternator/3G-ALT_wiring.gif
7. I am also following the guidelines from: Ford Fuel Injection 3G Install Tech

My alternator is exactly like the one pictured in the last link above.

Anyway, after my first start up of the car with the EFI swap I knew I would have a few bugs to work out. But this one has me stumped. I don't hear any squealing on the belt, car idles great. Everything seems fine but the Alternator gets really hot really fast. Probably would melt the belt clean off if I let it.

Any ideas???? Tonight I'm going to check for shorts and see if I have any major draw on the system. Other than that I can't figure it out.

Thanks in advance,

jrl

Thanks guys.. I will take my alternator to have it tested and test for shorts in the electrical system as well. What is the best way to test for shorts? I have a EZ2wire car harness and the other harness for the engine and computer. Bare with me, I'm a newbee to all of this and this is my first project car.

Thanks again for the feedback... Cheers, jrl

Well, I looked into my issue again lastnight.. Here it goes.

1. Checked my wiring setup again and still confident I have everything wired correctly.
2. Checked the Alternator and made sure the charge cable had no contact to the body of the alternator housing.
3. With the positive battery cable on the positive terminal and the negative disconnected (Key in Off position) I used my Ohm meter to see if there was a short between the positive and multiple ground positions on the frame and various bolts. No buzz/beep from my ohm meter.
4. I then disconnected the positive from the battery, turned the key to the ON position and took my Ohm meter probes to the main power cable of my harness and probed the grounds again. This time I got a beep. Not sure which wires are grounding but will probe more tonight. Once again, I'm new at this.

The beep that I got in number 4 above... Is that normal? My gut says yes but I'm a little suspicious of it. Any suggestions are well appreciated..

To answer the questions from HISIN50:

1. I don't think the belt is slipping. The pulley on the Alternator runs very smooth and turns easily. I'm using a regular 5.0L 302 Belt Tensioner and the belt's tension feels just right.
2. The 3G Alternator that I bought is one that has been rebuilt. It does have a silver/chrome paint on the outer shell. The inside guts look brand new.

I think I'm going to yank it out tonight and have it tested as soon as possible. I can't stop thinking about it and its driving me nuts when I can't resolve what appears to be a relatively common issue.

Thanks again everyone,

jrlayton