Alternator Problems on 5 Ton

[bbbang]

I am having problems with my alternator on my M813A1. It was producing voltage off the charts. I pulled it and took it to the local shop to get it rebuilt. They have rebuilt it but still can't get the voltaqe problem solved. Is their a source that someone would recommend to purchase a new or successfully rebuilt unit for my truck. Thank you.

 

[maddawg308]

There is a place in MVM that I have purchased a rebuilt unit from. Worked great! Their company is CME Armature, in Miami, FL. High prices, but they do great work. No website, and their phone numbers are in the MVM, I don't know them off the top of my head.

 

[vtdeucedriver]

Just wondering, did you try to adjust the voltage???????

 

[70deuce]

Ditto on the question of adjusting the voltage. Its extremely easy.

 

[emmado22]

Which genny is it? Whats the info on the dataplate?

 

[martinsaunders06]

?can you tell us how to adjust voltage on the cummins alternator as mine the same with the gauge showing max voltage with needle at top of scale?thought id read it was not adjustable in tm?

 

[vtdeucedriver]

If its the standard alternator, which it should be for all M series vehicle like the deuce and 5 ton. There is a small plug that has a allen head, unscrew the plug and inside is a small slotted screw................if I remember right, counter clockwise reduces voltage.

 

[bbbang]

Alternator Problems on 5 ton

Thank you for the info on reducing voltage. I will get with my rebuilder and see if that solves the problem.

 

[vtdeucedriver]

RE: Alternator Problems on 5 ton

forgot to mention, plug is under the wire connector cover.

 

[70deuce]

The allen head plug that provide access to the voltage adjusting screw on both my 1970 M35A2 and my 1972 M818 are not under the wire connect cover as the manual I think states. They are both accessable by just opening the hood. See pics. The allen head plug is right below the alternator's harness conection cover. Have adjusted both to 28 volts

Phil

 

[cranetruck]

As usual, PS magazine is pretty crystal on how things are to be done.....

 

[SLOrazorsedge]

I've been having inconsistent voltage spiking issues on my M936A1. Not having a volt meter, I found an excuse on spending $150 on a Fluke meter, nice to have something broken as an excuse to buy a nice tool!

Anyway, after charging each of my Hawker AGM batteries independently and testing each to ensure that I didn't have a dead cell, it was on to the alternator issues. My volt meter would show my alternator voltage after starting the truck at 28-29 volts fluctuating up and down. Once the truck was warmed up for a few minutes, I brought the RPMs up to 1500 RPMs per test parameters. Within a couple of minutes, my truck voltmeter would spike hard right into the red. Indicated voltage on the Fluke was in the 35-36V range. Immediately shut the truck down.

Thanks to the prior posts, I located the allen-head plug which is a 5/32" SAE. I removed the plug and due to the cooling system piping, you cannot see into the hole or use anything but about a 3" long probe. Using a mirror, flashlight and standing on my head, I could see that the voltage regulator adjustment screw was a medium phillips head. We used a long shaft 3" Milwaukee Phillips head driver bit with an end wrench to turn the driver. Restarted the engine and brought up to 1500 RPMs turning the adjustment screw entirely CLOCKWISE to the limit to REDUCE voltage. The screw only has 300 degrees of total adjustment per manual. Rechecked voltage meter and the alternator was producing in the 25.5V range.

Adjusted voltage COUNTERCLOCKWISE to increase. Voltage initially was perfect at 28.5V range. Watched the truck voltmeter after a few minutes it spiked to the extreme edge of the green/red line. Rechecked voltage which ranged from 30.5/31Vs. Readjusted the voltage screw down to full stop CLOCKWISE. Basically no help on the adjustment. The Fluke showed pretty consistent 30.5/31Vs. The truck voltmeter remained on the green/red white line. At least It wasn't pegged hard right into the red....So I suppose that means my alternator voltage regulator needs replacement? Anyone else have similar experience or advice prior to replacing the voltage regulator? Sorry for being long winded.

 

[74M35A2]

Sounds like voltage regulator is bad or going bad. They are available separately. Electronics typically start to flake out when hot before total failure. Also, I notice my voltage gauge goes high if I accidentally shut the battery switch off before the engine on my 925A2. Not sure if this is a back-feed issue in the gauge, or if voltage really goes too high, but make sure power going to the regulator is not dropping out, causing this.

 

[SLOrazorsedge]

Thanks brother. That's my next step or possibly do the Delco Remy SI alternator modification. I've been a motor head since I've been a kid, I've just never seen an alternator voltage regulator "linger" like this before. They're either OK or bad...:0(

 

[Munchies]

Ithink Jesusgatos (Jesse) has been having alternator issues on multiple 5tons. Try to PM him and see if he came up with a fix.

I see your in socal, you may already know this then so sorry if you do

 

[IsaLandr]

I just want to say thanks to the guys posting in this thread. My M923 has been pushing slightly low voltage for a few weeks now. Followed the information in this thread, adjusted the voltage regulator, and it's working just fine now, charging right where it's supposed to be.

Thanks, guys!

 

[SLOrazorsedge]

Thanks Munchies, I'll chat up Jesse. It's nice to see that this revised thread is still helping guys out and the procedures resulted in success for some guys :0). We fired up the wrecker today and loaded up two NOS MT654CR trannys in their steel shipping crates onto a M116A3 flatbed trailer. Thats a total of 2,000 pounds on one of these little trailers and it didn't even groan, amazing.

It was interesting watching the wrecker voltmeter, it would spike to the 31V range warmed at an idle. When we engaged the crane and the IP kick-down ramped up the RPMs to 1600, the voltmeter ranged down and settled on the low side of green (circa 26Vs). We ran the wrecker crane off and on for about an hour moving other heavy green machine stuff w/o any spiking issues. Its simply got to be a bad voltage regulator. We'll source one out and replace it and report on the result.

 

[jarhead1086]

Is there an aftermarket regulator that is more robust or reliable than these OEM ones? Like to buy two, one to replace in and one for a spare to prevent burning up the ABS ECU and other stuff I am planning on adding.

 

[74M35A2]

Is there an aftermarket regulator that is more robust or reliable than these OEM ones? Like to buy two, one to replace in and one for a spare to prevent burning up the ABS ECU and other stuff I am planning on adding.

An alternator voltage regulator is just a FET (Field Effect Transistor), which is just a simple switch. It is simply commanded opened or closed, based upon if the measured voltage is above/below the set point, respectively. From there, it is sending current through the brushes and into the alternator rotor, in the amount of several amps, to generate a spinning magnetic field.

I don't see why one could not graft a Delco 24V regulator onto our common 60A 24V military alternator. New Delco 24V regulator units are $15 on eBay. Is this a kit I should be offering?

 

[SLOrazorsedge]

I think the remedy to alleviate the voltage regulator issues on the 24V MV OEM alternators is the Delco Remy SI 24V alternator modification. There are a number of threads here on the modification. A one wire hook up and an aftermarket pulley on the Delco to spin it faster is simply years advanced in technology from the ole Leece Neeville alternators. Eventually that will be my solution.