Is this alternator defective?

[Robtstee]

First, I know how to test an alternator for function. I am concerned with connecting this alternator. Had a problem and burnt all the fusible links and smoke came out of Gen 2. Fixed all the links and installed a new alternator. Marked all wires when disconnected. It is wired per the diagram. Have tested for negative terminal isolated from case. Went to put on Bat 2 negative, got sparks. Disconnected and traced till I found the + term on Gen 2 to the 24v Buss was causing the sparks. With all wires disconnected except the neg terminal I've got 12v on the neg terminal, 12v on the exciter tab, 12v on the wire to the 24v buss and 12v on the little pin. Exciter wire 0v with key off, 24v on. New alternator, but the situation was the same with the old one. This may be all be normal but, I am unfamiliar with this setup and would like to know for sure before burning anything else up. Thanks in advance.

 

[Mullaney]

First, I know how to test an alternator for function. I am concerned with connecting this alternator. Had a problem and burnt all the fusible links and smoke came out of Gen 2. Fixed all the links and installed a new alternator. Marked all wires when disconnected. It is wired per the diagram. Have tested for negative terminal isolated from case. Went to put on Bat 2 negative, got sparks. Disconnected and traced till I found the + term on Gen 2 to the 24v Buss was causing the sparks. With all wires disconnected except the neg terminal I've got 12v on the neg terminal, 12v on the exciter tab, 12v on the wire to the 24v buss and 12v on the little pin. Exciter wire 0v with key off, 24v on. New alternator, but the situation was the same with the old one. This may be all be normal but, I am unfamiliar with this setup and would like to know for sure before burning anything else up. Thanks in advance.

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Gen 1 and Gen 2 are different (or should be different from a normal Chevy alternator). Both must have an Isolated Ground and that is pretty important. Picture attached



EDIT: Both Alternators are isolated ground and Both are the same. Thanks for the correction MarcusOReallyus

 

[porkysplace]

First, I know how to test an alternator for function. I am concerned with connecting this alternator. Had a problem and burnt all the fusible links and smoke came out of Gen 2. Fixed all the links and installed a new alternator. Marked all wires when disconnected. It is wired per the diagram. Have tested for negative terminal isolated from case. Went to put on Bat 2 negative, got sparks. Disconnected and traced till I found the + term on Gen 2 to the 24v Buss was causing the sparks. With all wires disconnected except the neg terminal I've got 12v on the neg terminal, 12v on the exciter tab, 12v on the wire to the 24v buss and 12v on the little pin. Exciter wire 0v with key off, 24v on. New alternator, but the situation was the same with the old one. This may be all be normal but, I am unfamiliar with this setup and would like to know for sure before burning anything else up. Thanks in advance.

CUCV Alternator Isolated Ground Therory of Operation

Sometimes we take things for granted. We assume everyone can wrap their head around the concept of the isolated ground circuit and the associated battery wiring. Warthog had asked a fellow member Amphi for his input of the isolated ground circuit and he conducted an experiment. Here is his...

www.steelsoldiers.com

From the cucv hepful threads

CUCV Helpful Threads

FAQ http://www.steelsoldiers.com/showthread.php?20600-FAQ-Thread-for-CUCV-s STARTER CUCV Stock Starter Circuit http://www.steelsoldiers.com/showthread.php?129483-CUCV-Starter-Circuit CUCV Doghead Starter Relay Modification...

www.steelsoldiers.com

 

[Mullaney]

CUCV Alternator Isolated Ground Therory of Operation

Sometimes we take things for granted. We assume everyone can wrap their head around the concept of the isolated ground circuit and the associated battery wiring. Warthog had asked a fellow member Amphi for his input of the isolated ground circuit and he conducted an experiment. Here is his...

www.steelsoldiers.com

From the cucv hepful threads

CUCV Helpful Threads

FAQ http://www.steelsoldiers.com/showthread.php?20600-FAQ-Thread-for-CUCV-s STARTER CUCV Stock Starter Circuit http://www.steelsoldiers.com/showthread.php?129483-CUCV-Starter-Circuit CUCV Doghead Starter Relay Modification...

www.steelsoldiers.com

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Thanks porkysplace !
That is a lot better than the little offering that I posted for Robtstee

 

[Guruman]

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Gen 1 and Gen 2 are different (or should be different). Alternator 2 must have an Isolated Ground and that is pretty important. Picture attached

View attachment 861033

It might also be worth mentioning that I've seen alternators that have this bolt/connector, but were NOT really isolated ground. If you have continuity between that bolt and the metal alternator body, it's NOT isolated.

I've also had folks get twisted up with the nomenclature of "isolated ground" when indeed that connection on gen2 does not go to ground, but rather 12v positive.

Good luck.

 

[Robtstee]

Thanks for the fast help, I read the article, but I think my question is more about the alternator than the system. I verified the Negative terminal on Gen 2 is isolated from the case with a known good meter. Verified the negative terminal on Gen 2 is getting 12v from the diamond on the firewall. The only wire connected to Gen 2 presently is the negative terminal(12v). So my question is it normal to have 12v on the Gen 2 positive terminal(disconnected) and the Gen 2 exciter tab(disconnected) with only the negative terminal(12v) properly connected? If so, that would explain the sparks when I put the rear Battery ground on. Thanks again

 

[Tow4]

Both alternators should be isolated ground if they are original to the vehicle. If you are not sure if the alternator works, take it to be tested or follow the testing sticky at the top of the CUCV forum and just connect the alternator directly to the appropriate battery as described in the test.

 

[MarcusOReallyus]

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Gen 1 and Gen 2 are different (or should be different).

No, no, no. They are identical from the factory. If they are different they are NOT stock.

 

[Robtstee]

To anyone who is in the same situation I was: I was asking if it was normal to get some sparks when hooking up the rear batt neg cable and normal to have 12v on gen 2 + terminal with that wire disconnected. Knew how to wire it up, knew how to test it for output, was afraid to connect it and burn the links up again. I took all wires off both alternators and checked and compared continuity and resistance between every connection. They all matched, figured there was no short in the new one, hooked them both up and all was good. Hope this helps someone.