M35A3 Alternator Problem

[glcaines]

The Prestolite alternator in my M35A3 has been declining for a few months. The needle is now firmly in the yellow on the gauge. I checked the voltage with my meter. The alternator is putting out 27 VDC regardless of the engine RPM. Then I discovered something interesting. The data on the label has been tampered with. According to the model, etc. the alternator should be a 60 amp. However, the label has 30 amp stamped on it. The 30 was an original stamp. Someone tried to obliterate the 30 by scratching it out but it is still legible. In addition, the S/N has been scratched out and a new S/N hand engraved. The rest of the label is pristine. AMA5104UT alternators are supposed to all be 60 amp from Prestolite. I would have assumed that the alternator was original from AMG. When I got the truck, which is a 1998 model, it only had a little over 3,000 miles on it. I believe the original mileage because the truck looked new inside and out. It even still had most of the black plastic covers on the seats from AMG when I picked it up at Fort McCoy. The GL Rep at Fort McCoy told me the mileage was accurate. The truck now still has only 13,536 miles on it, but it is 22 years old. There are several possibilities as I see it.

1. Prestolite converted a 30 amp alternator to 60 amp prior to delivery to AMG
2. Prestolite supplied a 30 amp alternator to AMG and tried to hide it by scratching out the 30
3. AMG replaced the alternator for some reason with one they had in stock prior to delivery to the Army and defaced the 30
4. The Army replaced the 60 amp alternator with a 30 amp alternator and whoever did it tried to cover it up be defacing the 30

I'm going to remove the alternator and try to repair it, but first I need to find documentation on rebuilding the alternator. I will also need to find out if the alternator is actually a 30 amp or 60 amp model. Actually, I'll try to adjust the voltage first.

 

[NDT]

5. Some clown at Prestolite stamped it wrong after a long weekend of drinking

 

[HDN]

That is fascinating! I need to do some electrical troubleshooting myself which may involve pulling the alternator out of the truck next year. I'll be sure to check for this. I can't remember the manufacturer off the top of my head, but it has the sunburst-style heat sink on the back.

 

[Sgt Jiggins]

Wish I still had the old one I just replaced - it was toast. Contacts under the cover were arcing. Surprised it didn't catch fire. New one is working flawlessly.

 

[bj1104]

I needed a new one a few years ago. I looked around and the cheapest i could find was a rebuilt from oshkosh at $550. I contacted www.cmearma.com via email and their prices were super low. This is a clip of the email from them with the prices
We have them available:
New: 425.00 ea
Rebuilt outright: 295.00 ea
Rebuilt exchange: 225.00 ea
Plus shipping/freight.
UPS Ground is 30.23 to zip 15212.

 

[glcaines]

Finally got around to do some troubleshooting. I measured the output with a VOM and it was putting out ~1 volt at 1200 RPM and the headlights on. I adjusted the alternator output and the max I could get was ~2 volts. I'm now looking for a replacement or a place that will rebuild it.

 

[HDN]

Yeah, that sounds like a voltage problem! An auto electrical shop should be able to help you out. My dad took a pair of generators out of M37s to the local guy, and they were perfectly rebuilt.

 

[microjeep]

Kayes Auto Parts (NAPA) in Blue Ridge, you can drop it at the Blairsville location if more convenient. Every time I take something there I'm amazed how cheap it is and Keith will fix it or let you know why he can't no BS.

 

[glcaines]

Kayes Auto Parts (NAPA) in Blue Ridge, you can drop it at the Blairsville location if more convenient. Every time I take something there I'm amazed how cheap it is and Keith will fix it or let you know why he can't no BS.

Thanks Mike! I need to get it fixed before the GA Rally. Otherwise I will need to drive my FLU419 SEE at 30 mph! No way.