New Member 1984 m1010 charging issue

[Therealgooz]

Hello, been lurking for a while and finally decided it’s time to participate, and hopefully get some help. I’ve just purchased a 1984 m1010 with 8k miles on the odometer. It fires right up and runs great. It was owned by a police department and the rear box was well kept.

Unfortunately it has a charging issue I’m trying to track down. The rear battery doesn’t seem to charge. At some point the DUVAC was removed but the truck is still running 12V/24V with both batteries wired in series. The top alternator has been replaced by a 12V alt and the old bottom 24V is still in there. My original plan was to do the full 12V conversion to solve the issue but recently noticed that both batteries are are rated for 650cca. Lower than the recommended 800+ cca. Can this be contributing to the battery not being able to hold a charge?

This is my first CUCV and my electrical knowledge is pretty limited. Any and all hell would be appreciated. Thanks

 

[dependable]

The lower rated battery is not contributing to the problem, as long as they are matching. I would recommend testing the voltage coming into each of the batteries while it is running to see what is going on. Seems like you have sort of a hybrid or half conversion of the 1010 system, with 1 12V and 1 24V bat. This may not be the problem, but it may be suspect.

I converted my 1010 to a 1008/1028 sysetem and that works well, there is also another conversion mentioned a lot on this forum for those who still wanted to keep ability to run the compartment AC. I think it was refered to as the Plan B conversion if you want to search it.

 

[Therealgooz]

The lower rated battery is not contributing to the problem, as long as they are matching. I would recommend testing the voltage coming into each of the batteries while it is running to see what is going on. Seems like you have sort of a hybrid or half conversion of the 1010 system, with 1 12V and 1 24V bat. This may not be the problem, but it may be suspect.

I converted my 1010 to a 1008/1028 sysetem and that works well, there is also another conversion mentioned a lot on this forum for those who still wanted to keep ability to run the compartment AC. I think it was refered to as the Plan B conversion if you want to search it.

thanks for the reply. Was hoping new batteries would be an easy fix. When I bought it the seller tested the batteries for me and the front was at 12ish volts and the rear at 24V but I’ll recheck them. Definitely some sort of hybrid system. I’m torn on whether to do the full 12V but looks like it might be the way to go.

 

[chevymike]

He did not say test the batteries but check the output of alternators (" testing the voltage coming into each of the batteries "). My guess is the lower alt is not putting out the right voltage/current. It should be close to 28v.

When I bought my current one, it was converted to "Plan B" and both alts were replaced with 12v. They way it is wired, it allows each battery to be charged by each alt but still keeps the 24v connection for the starting system. I am getting ready to fully convert over to 12v. My first M1010, I did this conversion because both alts were bad. I replaced the top one only and wired the batteries to be a 12v system (put them in parallel). At this point I was only using one alt to charge both batteries (no different than a civilian truck). This worked great and I removed the lower alt and never added it.

If you have a single 12v alt that is rated to 150amps or more, you can wire the system as a 12v setup and just use the one you have. You will need to change the starter to a 12v version, if it is still the original 24v system. If you are not using the rear A/C or heater, then you don't need to keep the 24v system. If you are, then you will need to replace the lower alt with another 24v one.

 

[Therealgooz]

He did not say test the batteries but check the output of alternators (" testing the voltage coming into each of the batteries "). My guess is the lower alt is not putting out the right voltage/current. It should be close to 28v.

When I bought my current one, it was converted to "Plan B" and both alts were replaced with 12v. They way it is wired, it allows each battery to be charged by each alt but still keeps the 24v connection for the starting system. I am getting ready to fully convert over to 12v. My first M1010, I did this conversion because both alts were bad. I replaced the top one only and wired the batteries to be a 12v system (put them in parallel). At this point I was only using one alt to charge both batteries (no different than a civilian truck). This worked great and I removed the lower alt and never added it.

If you have a single 12v alt that is rated to 150amps or more, you can wire the system as a 12v setup and just use the one you have. You will need to change the starter to a 12v version, if it is still the original 24v system. If you are not using the rear A/C or heater, then you don't need to keep the 24v system. If you are, then you will need to replace the lower alt with another 24v one.

ah I see. I’ll check the alts. And proceed from there. Currently the AC does not work but the heater does which is why I’m torn but I will most likely just complete the full 12V conversion if the bottom alt is not producing 28V. The seller included a new 12V starter so I already have that brand new in box. Last night I noticed one of my batteries is damaged and needs to be replaced. Do you see any issues buying a matching 650cca battery or would it Be best to upgrade both to 800+. Thanks and I follow your m1010 build on insta. Loving the custom gauge set up

 

[dependable]

It is always nice to have more cranking amps, but two matched 650s will likely meet your needs for the truck chassis, especially seeing you are in CA and not as likely to have to deal with very cold weather starts. If you have to replace one though, I'd get the highest amp set of batteries you can conveniently find. It does not pay to have unmatched batteries hooked together, whether in parallel or series.

If one of your battieries is damaged, that may be the problem right there. Just becasue seller mesaured a static voltage of 12V does not necessarily mean the battery is good.

 

[chevymike]

Thanks for the props on the gauges. Very happy how they came out.

Honestly, I would be looking to replace the batteries with higher CCA unless the ones you have are brand new. It sucks but if you need to replace one, I would replace both with the higher rated one. Sounds like you are just about there with the 12v conversion. Unless you are planning to use that heater a lot, which is going to require running the engine to keep the batteries charged, there are better heater systems designed for 12v use that take low power to run.

 

[Therealgooz]

It is always nice to have more cranking amps, but two matched 650s will likely meet your needs for the truck chassis, especially seeing you are in CA and not as likely to have to deal with very cold weather starts. If you have to replace one though, I'd get the highest amp set of batteries you can conveniently find. It does not pay to have unmatched batteries hooked together, whether in parallel or series.

If one of your battieries is damaged, that may be the problem right there. Just becasue seller mesaured a static voltage of 12V does not necessarily mean the battery is good.

Batteries are newer and I honestly don’t know if it was already damaged when I bought the truck. Regardless I’ll be upgrading both at once And processing from there. Thanks for the input

 

[Therealgooz]

Thanks for the props on the gauges. Very happy how they came out.

Honestly, I would be looking to replace the batteries with higher CCA unless the ones you have are brand new. It sucks but if you need to replace one, I would replace both with the higher rated one. Sounds like you are just about there with the 12v conversion. Unless you are planning to use that heater a lot, which is going to require running the engine to keep the batteries charged, there are better heater systems designed for 12v use that take low power to run.

yeah they were basically new but looks like I’ll just upgrade to newer higher rated batteries. Good to know about the heater. I’ll probably be selling my current one when I make the switch to full 12V if anyone in SoCal is interested.

 

[chevymike]

yeah they were basically new but looks like I’ll just upgrade to newer higher rated batteries. Good to know about the heater. I’ll probably be selling my current one when I make the switch to full 12V if anyone in SoCal is interested.

If you find anyone interested in the heater... have them talk to me too. I have two of them I will give away.

 

[Mad Texan]

ah I see. I’ll check the alts. And proceed from there. Currently the AC does not work but the heater does which is why I’m torn but I will most likely just complete the full 12V conversion if the bottom alt is not producing 28V. The seller included a new 12V starter so I already have that brand new in box. Last night I noticed one of my batteries is damaged and needs to be replaced. Do you see any issues buying a matching 650cca battery or would it Be best to upgrade both to 800+. Thanks and I follow your m1010 build on insta. Loving the custom gauge set up

Welcome!

The bottom alternator does not have to be replaced with another 24v one. You can use another 12v alternator. There is a lot of good information about this here: DUVAC Removal Plan 'B'

And I have two 24v alternator's from my conversion. My heater went away a week or so ago...

 

[Therealgooz]

Welcome!

The bottom alternator does not have to be replaced with another 24v one. You can use another 12v alternator. There is a lot of good information about this here: DUVAC Removal Plan 'B'

And I have two 24v alternator's from my conversion. My heater went away a week or so ago...

tHank you!
I’m currently reading through the plan B thread to try to get an understanding of how my ambulance was rewired. I will be tracing wire and checking voltages tonight. It’s a slow process for me. My electrical knowledge is limited but I’m learning a lot thanks to this forum. I’ll report what a find and how a remedy the problem.

 

[Therealgooz]

update: tested the alts looks like the 24V alt is failing. Need to recheck all connections but looks like I’ll be making the move to full 12v. Thank you to people who helped

 

[41cl8m5]

Just letting you know the glow plug system will only operate on 24v as wired. Also the starter system is also 24v so there will need to be replacement of a relay under the dash as well as the starter. Also the albulance box runs on 24v so you will lose the overhead light operation. The fans for the a/c will run very slow on 12v and the multi fuel heater in the rear of the box will be inoperable but the way the military had it spec'ed out for the wiring it never worked anyway (big secret most don't know, unless you have an understanding how the heater system needs to be wired up in the first place).

Just letting you know the can of worms your looking into before you get started. In know way am I trying to change your mind on your plans are with your truck.

 

[Therealgooz]

Just letting you know the glow plug system will only operate on 24v as wired. Also the starter system is also 24v so there will need to be replacement of a relay under the dash as well as the starter. Also the albulance box runs on 24v so you will lose the overhead light operation. The fans for the a/c will run very slow on 12v and the multi fuel heater in the rear of the box will be inoperable but the way the military had it spec'ed out for the wiring it never worked anyway (big secret most don't know, unless you have an understanding how the heater system needs to be wired up in the first place).

Just letting you know the can of worms your looking into before you get started. In know way am I trying to change your mind on your plans are with your truck.

thanks for the heads up. I’m aware of glowplug and starter changes I will also need to make. The previous owner included a new 12V starter he had purchased when he planned to convert it himself. I pulled the 24v alt today. I’m hoping to keep this fix as simple as possible. If I can reasonable source a 24v starter I’d prefer to keep the 12/24v system.

 

[Therealgooz]

Update: took the 24v alt to a an alternator shop and it came back good. Put it back in and I’m seeing 14 volts at the top 12v alt and 26ish from the 24v alt. Is this the correct voltage or should I be seeing it closer to 28v when on at the lower alt? Thanks

 

[41cl8m5]

It depends on the condition of you batteries and there ability to hold a charge. On a 12 volt system an alternator producing a voltage above battery voltage is almost always looked at a good indicator that the alternator is working ok. Usually most alternators in a 12 volt system will max out around 13.5 volts but the voltage is not the only factor you also need amperage and that is why all new vehicles use alternators instead of generators today. They are a lighter in weight so they can be designed to be bigger in amperage output without becoming gigantic. Now the system is in a closed circuit with the batteries and depending on there condition the batteries can act like a sink or a resistance to the voltage from becoming full potential of the 24 volt alternator. Now on the firewall there are two power bars one is for 12 volt and the other is for 24 volt I believe, also there is a diode between the two and if this diode is shorted or open this will also cause you issues. Other basic stuff like unseen corrosion on the battery terminals will add confusion.

Basically the 24 volt 100 amp alternator should be able to get up to about 27.8 volts if you are using the original one for the M1010. But like I said there could be reasons within the circuit that could keep the alternator from only giving you 26 volts.

There is one other thing when you are running two different alternators with two different voltages if your sizing of the pulleys the amateur and the coils are not the same you could get some goofy feedback readings on some multimeters due to the grounds are common on both, to help with this just make sure you use the ground of the case of the alternator and the power output of the same alternator, sometimes even reverting to a old school dial multimeter instead of a digital one will help.

 

[chevymike]

Just for reference on the 12v side, normal charging voltage is 13.8 to 14.2 volts. 24v side would be 27.6 to 28.4 volts.

Where are you checking your voltage? Is it at the alt output terminal or actually at the battery post? Verify at those two points and they should be within .2 volts. If your alt output and battery post are showing .5 or more voltage loss between the two, then you likely have some bad/dirty/loose terminal connectors. If you are getting close to the same reading but is still showing much lower voltage, it could be an issue with a cell going bad in the battery and not allowing the alt to push the correct voltage.

 

[Skinny]

First post back after many years!

M1010's are cool but man do they suffer from neglect in the electrical department. I think you really need to figure out if you want to stay 24v or go 12v. Cannot proceed until you make that call.

24v is awesome for cranking power, jumping the other CUCV's, and staying original. That is where it ends.

Doesn't interchange to non-military vehicles, accessories are expensive, parts can be found but usually not locally.

You have a unique advantage with the M1010 accessory brackets that you can go 12v or 24v and have AC.

If you stay 24v, just install a pair of Leece Neville 555JHO 160a alternators in series. Yank all that Duvac stuff out. If you want to go 12v, you only need one alternator. 160a is plenty. You can use the bottom mount for a second circuit for like house loads or just keep it empty.

Doesn't get any easier then that. One word of caution. The lower radiator hose on the M1010 is unique to clear the lower alternator belt. You really can't find them so just cut the radiator side short so it gets pulled forward out if the way.





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