Prestolite Alternator

[Stkelsey]

I'm challenged with trying to test and see if I can determine if my alternator is charging my battery. I've read through the forum a coupleof times and my alternator doesn't seem to match the 'stock' description. I'm starting to think that I may have a aftermarket alternator that would have been replaced by the Fire department that owned the rig before I did. It's kind of hard to see the plate on the back of the alternator but I'm pretty certain it made by Prestolite. I can clearly see that the specs are 24V 42 Amp. I have tested the output and with the battery's disconected I'm only getting 24.6 volts. The charging gage never gets out of the yellow zone, so I know from reading the forum that I'm not really getting the recommended 28V charge while the engine is running. Anyone have any info on this particualr alternator? I'm going to geta picture of the alternator on the forum this weekend and hopefuly squint at the name plate, backwards with my inspection mirror to get the full model number of the unit. I do have an aftermarket battery charger hoked up to kep the battteries at full charge in between starts and running. My concern is if I'm out for the day and it won't fire up. I did experience a 'dead' battery a couple of weeks ago and that was the catalyst for checking the charging system.
??

[brute4c]

I dont know that one but stock is a 60 amp unit.

The mil ones have a cap plug that you remove and underneath is a small straight blade type screw. Turning this screw adjusts the output of the alternator up and down...a little goes a long way...if yours has this plug, remove it and see if you can adjust up to the proper 28.8 volt level.

Getting a 60 amp unit would probably be better...of course if this one will adjust and work for you for now...why not?

[Barrman]

The military had 25 amp external regulator generators. Then they switched over to the 60 amp internal regulator alternators. The M715 only came with the 60 amp alternator.

That being said, I have seen stock M715's with 3 different styles of 60 amp alternators. Some have the cooling fan at the rear, some about a 1/3 of the length from the rear and some about the middle. Basically, the military kept changing the design used and they have ended up on our trucks over the years.

There is a member here who rebuilds them. Several are on E-Bay each month also. You can also get a Delco 12SI style alternator in 24 V.

[brute4c]

I think they used at least 2 manufacturers....Leece Neville and Prestolite...thats part of the differences...the Prestolite may have been redeisgned thus giving another version...

Come to think of it, my truck had a Ford alternator on it when I bought it...very much looking ike the leece Neville type with the military FSN and all on the plate...same size and 60 amp output.

I have a couple styles out in the shop...maybe I'll post a pic someday...

[george walker]

I have noticed 2 designs of the military alt. one w/ the fan on front an one w/ the fan on the back, perhaps one is the leece an the other is the prestolite. about 10 yrs. ago I tried to have one rebuilt at an alt. shop an they said they couldnt get the parts something about the manufacturers werent allowed to sell the parts to other than the military and their approved sub contractors. Im not sure if its still the case nowdays, there was a place in fla. i think that advertised having them but they wanted like $450 for a rebuilt exchange unit or some outrageous price.

[brute4c]

One of our members takes cores and rebuilds them...all the way down to redoing the windings and epoxying in new diodes...wheres that info for him....

Some of his rebuild is here:

http://m715zone.proboards102.com/ind...9974046&page=1

Here is him asking for cores:
http://m715zone.com/vb/showthread.php?t=4471

[adk4x4]

One of our members takes cores and rebuilds them...all the way down to redoing the windings and epoxying in new diodes...wheres that info for him....

Some of his rebuild is here:

http://m715zone.proboards102.com/ind...9974046&page=1

Here is him asking for cores:
http://m715zone.com/vb/showthread.php?t=4471

Thanks for the plug Brute4c. I received little interest from the forum on rebuilding as it can more expensive than an ebay one from a take off yard. I would still venture a few exchanges for the group as I do have some parts sitting on the floor.

As for a history lesson, my investigations seemed to indicate that Leese-Neville and Presotlite have always have had a close if not contractural relationship in the alt business. Made by LN and packaged under the Presto name type deals and such. That's why most 715 alts have both names on them in most cases. As for the different models, the last digit is the most important one to look at on the model #. starting with A all the way to F, some looking different (fan position) and others having only internal differences. All things being different, they are all 28v 60amp alts (not Gens) with the same frame mounts. Even the initial hummer line carried the F version I believe until it was phased out completely and replaced with a new animal all together.

[Blitz]

Old thread.. just adding the manual for our units.
Rebuilt one tonight.


2920-909-2483

A0013002AD or A0013002AC probably on our trucks.
This manual covers about 8 models.

http://www.liberatedmanuals.com/TM-9-2920-225-34.pdf

[Blitz]

-34P manual...

http://www.pedros.cz/M151/TM_9-2920-225-34P.pdf