Is my alternator dead? 923A2

[TexAndy]

I picked up a truck without an alternator. That is to say, I had someone pick one up for me, and bought a pulled alternator from another truck they picked up.

It's kind of hard to tell from the TM whether I hooked it up correctly, tho. The diagram on 3-229 simply doesn't say which wires go where. I think I've got it right, simply by process of elimination, but I went ahead and took some pics anyways. Maybe ya'll can tell me if this is correct?

From top to bottom, the wires with ring terminals: Negative, Positive, 566. And 568 is the quick connect.

I'm hoping not, because the alternator does not seem to be putting out anything.

Battery voltage is about 23.9 with truck running or not (but battery switch on, in either case).

Measuring the positive wire of the alternator and ground gives a reading of 23.9 with truck running (low alternator voltage output test in TM) I've tried turning the voltage adjustment screw CCW per the TM, to no effect.


I've tried the "No output" troubleshooting on pg 2-120/121 of the TM, Test 2. Shown in picture.

That's measuring wire 568 from harness, disconnected from alternator, with positive DMM lead and ground with negative DMM lead. Reading shows battery voltage. According to the TM, the solution is "replace alternator."

I'm basically stuck. I don't know what to try next. Assuming I had the thing hooked up properly and assuming I was following the TM correctly (two very big assumptions), then it seems like my alternator is kaput. But since I REALLY don't know my way around alternator rebuilding (never done it), I figured I'd seek help here, first.

Ideas? I'd like to get this worked out so I can try to tackle the transmission, next. But I don't want to wear down the batteries while I'm doing so...

Any help ya'll could throw my way would be greatly appreciated.

 

[PETE BALLARD]

Many places that sell alternators will bench test your unit for you, usually at no cost.

 

[Suprman]

The regulator part on the end is replaceable. Southern auto wholesalers actually sells all the parts for the mil alternators. In my experience though, a bad regulator will usually cause high voltage not no voltage. No alternator places in my area have a setup to test 24v alternators unfortunately. If you find someone parting a truck maybe they can cut the wires and leave a few inches on the alternator.
Will

 

[TexAndy]

I don't know that the regulator is the problem, but thanks for the link.

I guess I'll ask around to see if anyone can test a 24V alternator.

 

[MtnSnow]

Here is some good info.....Pay attention to the pages 16 thru 19 but they are all good info dealing with Batteries & Alternators.

 

[TexAndy]

Here is some good info.....Pay attention to the pages 16 thru 19 but they are all good info dealing with Batteries & Alternators.

Good info. Thanks. The tests on the pages 16 through 19 are basically what I did. Makes me think there's a broken wire in/on the alternator itself.

 

[Keith_J]

Mark had an alternator that failed dead, swapping regulators brought it back to life. Such is the nature of transistors, they either fail closed (over voltage in this case) or fail open (dead alternator).

 

[davo727]

How about the guy that sold you the dead alternator swaps it out to a good one for you?