jamesgrizzlyadams
Observer
DUVAC Removal "Plan B"
A commonly known weak point in these M1010’s is the Dual Voltage Alternator Controller (DUVAC). It’s made up of two components: the voltage regulator and the DUVAC box. From what I gather, the main function of this mysterious blue box is to take the 27-28V input from the top 24V 100A alternator, and step it down to ~14V to charge the front battery. For those that are unfamiliar with the M1010 24V system: it’s basically two 12V batteries in series, where the 24V load is taken from the rear battery +ve terminal, and 12V loads taken off the front battery +ve terminal. There are two 24V alternators, the bottom alternator charges both batteries in series at ~27V and the top alternator charges just the front battery at ~14V via the DUVAC to handle the various 12V loads. One plausible explanation for the 24V system, was to allow the CUCV's and other vehicles to boost a larger vehicle if needed (think 5 ton, armoured etc). For visual people, here's the charging system wiring diagram from the manual :Wow1:
After driving my new truck home and excitedly showing everyone how the A/C unit and heater works, flicking the spotlights on and off etc, the batteries had run down to the point that the truck wouldn’t start. I decided I’d boost it and take it out for a little spin to give the batteries a bit of a charge. Well, I didn’t make it far before the truck quit on me, the voltmeter was just dropping and dropping until the truck shut off a few blocks away. After getting another boost from a friendly and curious neighbour I limped my way back home.
As an aside, if you get one of these vehicles, make sure you think about what you’re doing when you go to boost it from a normal 12V vehicle. Common sense, but easy to forget: if you’re boosting the rear battery (24V at +ve terminal) you must connect your jumper cables from the 12V vehicle directly to the +ve and –ve terminals of the rear M1010 battery. If you put the cable on the +ve terminal and the engine block you’re hooked up to 24V! Bad! So basically, you need two good, isolated, 12V batteries to boost the M1010 which might mean two other 12V vehicles.
I decided it was time to dig into the electrical system to see what the problem was, and why my batteries were seemingly receiving no charge from the alternators. Instead of trying to deal with the DUVAC, I decided I would do what many M1010 owners have done and just get rid of the damn thing. I didn’t want to do a full 12V conversion as I would like to use the existing A/C and heater for the time being. I was also advised by my uncle, who works with large diesel engines (marine, generators) to keep the 24V starting system as he says it’s the way to go, especially in cold weather. For these reasons I decided to give the DUVAC REMOVAL PLAN B method a try. Another bonus with this method is that, should I decide to completely convert to 12V in the future, I’d already have a 12V alternator installed.
I ordered a LEECE-NEVILLE 12V 160A alternator on ebay, and started with the DUVAC removal. Man, this DUVAC thing was a mess. From what I had seen online, most people just tape and fold back all of this wiring. I didn’t like the idea of having a rats nest of unused wiring hanging under the hood, so I went all in and cut open the main wiring bundle, discarding the old grungy heat shield and tape.
A commonly known weak point in these M1010’s is the Dual Voltage Alternator Controller (DUVAC). It’s made up of two components: the voltage regulator and the DUVAC box. From what I gather, the main function of this mysterious blue box is to take the 27-28V input from the top 24V 100A alternator, and step it down to ~14V to charge the front battery. For those that are unfamiliar with the M1010 24V system: it’s basically two 12V batteries in series, where the 24V load is taken from the rear battery +ve terminal, and 12V loads taken off the front battery +ve terminal. There are two 24V alternators, the bottom alternator charges both batteries in series at ~27V and the top alternator charges just the front battery at ~14V via the DUVAC to handle the various 12V loads. One plausible explanation for the 24V system, was to allow the CUCV's and other vehicles to boost a larger vehicle if needed (think 5 ton, armoured etc). For visual people, here's the charging system wiring diagram from the manual :Wow1:
After driving my new truck home and excitedly showing everyone how the A/C unit and heater works, flicking the spotlights on and off etc, the batteries had run down to the point that the truck wouldn’t start. I decided I’d boost it and take it out for a little spin to give the batteries a bit of a charge. Well, I didn’t make it far before the truck quit on me, the voltmeter was just dropping and dropping until the truck shut off a few blocks away. After getting another boost from a friendly and curious neighbour I limped my way back home.
As an aside, if you get one of these vehicles, make sure you think about what you’re doing when you go to boost it from a normal 12V vehicle. Common sense, but easy to forget: if you’re boosting the rear battery (24V at +ve terminal) you must connect your jumper cables from the 12V vehicle directly to the +ve and –ve terminals of the rear M1010 battery. If you put the cable on the +ve terminal and the engine block you’re hooked up to 24V! Bad! So basically, you need two good, isolated, 12V batteries to boost the M1010 which might mean two other 12V vehicles.
I decided it was time to dig into the electrical system to see what the problem was, and why my batteries were seemingly receiving no charge from the alternators. Instead of trying to deal with the DUVAC, I decided I would do what many M1010 owners have done and just get rid of the damn thing. I didn’t want to do a full 12V conversion as I would like to use the existing A/C and heater for the time being. I was also advised by my uncle, who works with large diesel engines (marine, generators) to keep the 24V starting system as he says it’s the way to go, especially in cold weather. For these reasons I decided to give the DUVAC REMOVAL PLAN B method a try. Another bonus with this method is that, should I decide to completely convert to 12V in the future, I’d already have a 12V alternator installed.
I ordered a LEECE-NEVILLE 12V 160A alternator on ebay, and started with the DUVAC removal. Man, this DUVAC thing was a mess. From what I had seen online, most people just tape and fold back all of this wiring. I didn’t like the idea of having a rats nest of unused wiring hanging under the hood, so I went all in and cut open the main wiring bundle, discarding the old grungy heat shield and tape.
