Alternator Rebuilt and now Voltage Gauge in Red?

[Grantshire]

Ok, finally chased down the alternator/Gen1 issue on my daughter's M1009, driver's side alternator was bad. Had it bench tested (the right way) to confirm, then rebuilt and it is back in the truck. Gen1 light goes off now as it should but the gauge is acting different. When it is idling the gauge is where is should be but as soon as you accelerate it moves into the red on the far right side of the gauge. Any thoughts on what is causing this?

 

[simoncrk]

Mine was doin the same thing, Ive got my Gen in the pick up to take the repair shop. Im hopin they can rebuild it. Did you tell them its off of a 24 volt system when they rebuilt it?

 

[Alredneck]

THe alts are both 12v. You can buy them new for $130 or so at your local parts house. OP it sounds like a voltage regulator is the problem. I have had the same issue on a 5ton but different electrical system. As I am still learning the CUCV systems I would let one of the gurus post up about how the charging system controls voltage to each battery. There are 12v and 24 volt systems in the CUCV and why the GOVT did one way or the next is beyond me at this moment.

 

[Warthog]

. You can buy them new for $130 or so at your local parts house.

Not so. Most parts houses don't carry the "isolated ground" alternator. Napa does carry the Wilson remanufactored alternaternators for $220, but even they are having issues with the rebuilds

http://www.steelsoldiers.com/cucv/30839-caution-buying-wilson-alts-napa.html

 

[Warthog]

...you accelerate it moves into the red on the far right side of the gauge. Any thoughts on what is causing this?

Sounds like you have a bad regulator in one of the alts. I would guess the older one. They should be putting out ~14v each with the engine reved.

You can check it with a hand held voltmeter. First check across the batteries and then the alts themself.

If you have to replace the regulator, at least they are under $5.

 

[Alredneck]

If it is the recommended #7157 ( off the top of my head part # may be different ) that is in the parts reference section of the CUCV FAQ thread then yes you can get them at any Autozone or Advance. it may have to be ordered but they can still get them. I bought mine from my local Advance and if I remember currectly it was a stocked item. Different locals may be different. I was expecting a cheap $40 alt but it was like 3 times that. You can search the part number online before you waste you fuel going to the store.

 

[Warthog]

The 7157 is good replacement for the drivers side alternator only. It is a standard Cadillac alternator. It WILL NOT work on the passenger side without fireworks at the batteries or wiring harness.

The military used the "isolated ground" on both sides so they would only have to stock one type and it could be moved side to side if needed.

I am rebuilding an alternator and will be posting pics of what the "isolated ground" really is.

 

[Grantshire]

Thanks for all the advise and here is a partial update.

I had some Germans business associates stuck in the states due to the volcano in Iceland and could not get to the M1009 so I had my local mechanic do the alternator. You can kind of guess where this is going, but he swore up and down he knew how the military 12v/24v systems worked. He works on just about anything from tractors to semis to small cars. Anyway, I talked to him about it and he said he would check it out to see what was happening. Asked my daughter to stop by his shop on the way home from school Friday. Big accident on I-95 and she sits in traffic for over an hour and the shop is closed by the time she get there.

House is only three miles from the shop so figured we would run it up there on Monday. As she pulls into the driveway she hears a pop, gage drops back into the yellow area and the Gen 1 light comes back on. My guess is the new alternator fried but I won't be able to get it checked out before Tuesday at the earliest.

Stay tuned, not over until

 

[Grantshire]

All is well again!

Turns out she poped the - drivers side alternater belt on the way home. Went ahead a replaced them all but it was still pegging the gauge. Checked with the rebuild shop and they had put a 24 volt relay in the alternater. They ut the right one in and everthing is back as it should be.

 

[Warthog]

24v + 12v = 36v....... yep, I would say that the needle would be in the red....Glad you got it fixed.