12 volt conversion help

[taylorbsmith]

Hey guys i need a little help. I know this has been mentioned numerous times on here but I cannot look through the 700 plus threads that come up in my search. So be easy on me.

I have 87 M1028 and I am having a problem with the dual 24 volt alternators. The front battery is not getting charged. I have had the alternators rebuilt, and replaced both batteries. But the previous owner did something with the alternator wires so that the truck could run off of just one alternator. This is not working because the headlights are running the front battery down and its not getting charged back up. I think my best solution to this problem is to just convert the truck to 12 volts and be done with it. No more 24 volt alternators and no more equalizer! Any insight would be greatly appreciated.

 

[original]

The alternators are 12v not 24v. Your much better off repairing the 24v system as you have already had both alternators rebuilt. You also have the TM's and other members to guide you through the original system repair. Make your decision and add pictures of the wiring when your ready. I will try to help if your going to stay with the original system. Good luck, mate.

 

[Recovry4x4]

If it's really an 87 M1028 it may have the ambulance charging system. There are many threads dealing with this. I suggest using the terms duvac and M1010 in your search values. This is not as simple as the regular CUCV system. Can you provide a simple underhood pic? Before I type my backside off, I'd like to confirm that I'm not spewing into the wind.

 

[trukhead]

I have looked through previous threads on the topic. Aside from doing a search and looking through the TMs to determine exactly which charging system you have, try:

Cleaning the plastic 2 pin connectors and terminals for each alternator,

make sure the charging bulb indicators in the dash are good,

Try using jumpers to ground the chassis to the engine, engine to the body, driver side alternator to the engine to determine if the grounds are faulty.

The passenger side ALTERNATOR IS GROUNDED TO THE POSITIVE OF THE BATTERY BELOW IT!!!

In previous threads, contributors stated these fixes caused the charging system to work.

It is up to you to determine which charging system you have so consult the TMs for the wiring harness diagrams.

I'm just relaying what I read.

P.S. The stock typical non ambulance CUCV (M1008, M1009, most M1028 and maybe M1031) have 2 12 volt alternators wired in series to create 24 volts for the starting circuit, trailer light circuit and the power blocks up on the passenger side firewall. Most of the rest of the truck is 12 volt. A good VOM (volt ohm meter) is you friend with the CUCV.

 

[MarcusOReallyus]

I think your best solution to this problem is to find out what's going on. I sympathize with the desire to just make it simple, but it isn't that simple.

It's not going to be simple to convert it to 12 volts until you know what you have. That's the hard part - figuring out what is actually there, and what is going on with it.

Once you've done that, it's just as easy (and probably easier) to get it working correctly as it is to make it 12v.

Either way, the hard part is figuring out where you are now, and you can't do anything until you do that.


I think the best thing you can do is to grab the TMs to make sure what charging system the truck started with, then work through the appropriate troubleshooting to figure out what ain't working. Holler here and you'll get help with that process.

Once you've done that, and fixed whatever you find wrong, you'll find yourself with a good working 24v system.

Then you can decide to 12v it.

 

[taylorbsmith]

Hey guys thanks for the help. I heve done some research, and I have the two 24 volt leece neville alternators with the ambulance package. I have had a few m1009's and a m1008. I am familiar with the 24 volt stock system. But this system has me totally confused. any help would be great!

 

[Screamin' Metal]

As the military parts starts to dwindle and all, you can convert to 12 volt fairly easily. The only 24 volt parts on these trucks are the Starters. While I do love the 24 volt system, and they are not that hard to troubleshoot after you've been in the repair business working on these things for 10+ years.....they can get irritating at times, especially out in the field. They did retire these for a reason.
I'm gonna try and do a attachment here, bare with me....

 

[Screamin' Metal]

Also, do a search, theres a good article about the Forestry Service conversion, and if you do it EXACTLY as instructed, you will have -0- problems. I have done literally Hundreds of these....My own personal truck, a 84 M1009. Haven't have a problem starting her in over 6 years.