Hot alternator when charging battery

[David_L]

I was able to go-cart to the shop for my alignment and battery was completely dead. I hooked up my 6amp charger without disconnecting the battery cables. 4 hours later I noticed my alternator was hot or very warm but I could still touch it.. Just wondering if this is normal or maybe I wired something wrong?

This is a single wire alternator. Positive battery terminal, alternator wire and ignition wires are connected to starter solenoid. I do know I need to track down whatever drained the battery after battery is charged.

[Norm B]

The alternator should not be warm. It is supposed to shut off the field circuit when the RPMs drop at engine shut down. It will drain your battery pretty quickly if it doesn’t.

Norm

[CraigS]

I forget the specifics but there is a pack of diodes in there that should allow current to come out of the alternator but not flow the other way. I am thinking one of them is leaking. It may be the cause for both the hot alt and the dead battery.

[David_L]

I forget the specifics but there is a pack of diodes in there that should allow current to come out of the alternator but not flow the other way. I am thinking one of them is leaking. It may be the cause for both the hot alt and the dead battery.

Yea that's what I hink i read somewhere. The bad thing is the alternator is brand new.. Well from the start of my build anyway and a couple of starts.

[Just puttering]

If you cant warranty it, you can open it up and check the diodes with a meter. There are four diodes, they are big so easy to see and check!

Just searched an auto parts web site and they have diode packs listed.

[David_L]

If you cant warranty it, you can open it up and check the diodes with a meter. There are four diodes, they are big so easy to see and check!

Just searched an auto parts web site and they have diode packs listed.

I just finished testing it yesterday using the diode tester and here are the results. I think this is one or more bad diodes. It's a new build alternator but haven't heard back from Mike Forte yet. I'm find replacing the diode back but I don't see a parts number on the Alternator so not sure how to how I will find the correct diode pack? Going to pull off the alternator this afternoon.


This reading looks correct. Com or black lead on the alternator stud, red grounded on body
https://thefactoryfiveforum.com/attachment.php?attachmentid=187017&d=1688923981


This one shouldn't have a reading..
https://thefactoryfiveforum.com/attachment.php?attachmentid=187018&d=1688923981

[David_L]

Well no luck on warranty. Turns out this alternator is a GM 7127 style 100 amp. I'm not really sure what that style means as it dosn't seem as common. Also Black was hard to find(of course).

I did take it apart to see if I could replace the diodes but they don't make it easy as you have to take apart the case. The diodes are hidden behind a plastic cover that can't be removed as its behind the stator and the stator would need to be de solder to remove. I guess I could cut out the plastic cover to access the diodes?

I went ahead and ordered this on amazon so it should fit. Tuff Stuff 7127NF6G Alternator (100 Amp GM 1 Wire 6-Groove). I'm also assuming that a GM alternator can be wired up the same as a Fort style alternator? Does anyone know if a 7127 style alternator is a GM 10/12 DN/SI or CS130?

[Mastertech5]

If the diodes are soldered in then that alternator is not serviceable. GM went to those after the CS130, which I used to rebuild.

[David_L]

If the diodes are soldered in then that alternator is not serviceable. GM went to those after the CS130, which I used to rebuild.

Thanks. I took it apart again and was able to cut out the plastic diode/regulator. I can see the part diode part number and found it on Amazon, but as you can see it's soldered in. I see at least 4 soldered joints. I'm assuming this is what you are talking about? It might be possibe to remove but de soldering all the connections at once would be hard to do.. I've ordered a new tuff Stuff alternator and it should be here on Monday. Just hoping it will bolt up the same as this one! I also plan on switching out the pully to my black one. I should be able to do this with my impact wrench.

https://thefactoryfiveforum.com/attachment.php?attachmentid=187242&d=1689442397

https://thefactoryfiveforum.com/attachment.php?attachmentid=187243&d=1689442397