Hmmwv 12 Volt Conversion

[RayGunSlayer]

Hey guys, I was gonna see if I could get some information from someone. I have my truck torn apart right now trying to go through it and fix a lot of stuff on my extremely custom M1097A2. I was curious to see if anyone knew what it would take to convert my hmmwv from 24 volts to 12 volts? I know for a fact, the starter, the IP fuel solenoid, and a different alternator. My gauges are Speedhut gauges so they can run off of 12 or 24 volts already. Beyond that I do not know. The reason I am wanting to do this is because of the lower cost of maintenance in the long run when it comes to replacing parts and batteries and also because I have quite a few things already 12v on my truck and would like it all to be the same. Any information would be great!

 

[Coug]

the wiper motor seems to be the biggest hurdle from what I've seen in other threads/pages

 

[RayGunSlayer]

Well truthfully I don’t even have the wiper motor anymore so that part wouldn’t affect me thankfully. Do you know if the glow plug system and EESS box work fine being 12 volts?

 

[Mogman]

No they will not, you have to change everything that is 24Vm including the glow plugs and some means of controlling them, CAMO may be able to build you a custom EESS box for 12V, otherwise it is a massive re-wiring job, best to start over and re-wire the entire truck.

 

[RayGunSlayer]

Well to be honest with you I pretty much already have remade the entire wiring harness on the truck and that’s why I was thinking of doing this. My truck literally only has wiring for the glow plugs and EESS, IP, starter, alternator, engine temp on side of block, oil pressure sender, 4l80e transmission, and fuel sender. I’m not using any of the cooling fan hydraulic system so all of that is gone, no light system, etc.. It’s literally as bare basic as this setup could almost possibly be. Getting the glow plugs for a Chevy style 6.5 diesel wouldn’t be hard at all just changing the connector for the plugs. I wonder how hard it would be to have a custom EESS box made for 12v plus I’ve been looking the alternator part wouldn’t be that easy either. The starter would be easy as Power Master makes a 12v one for the civvy 6.5s and the IP solenoid would be really easy too.

 

[Milcommoguy]

Well to be honest with you I pretty much already have remade the entire wiring harness on the truck and that’s why I was thinking of doing this. My truck literally only has wiring for the glow plugs and EESS, IP, starter, alternator, engine temp on side of block, oil pressure sender, 4l80e transmission, and fuel sender. I’m not using any of the cooling fan hydraulic system so all of that is gone, no light system, etc.. It’s literally as bare basic as this setup could almost possibly be. Getting the glow plugs for a Chevy style 6.5 diesel wouldn’t be hard at all just changing the connector for the plugs. I wonder how hard it would be to have a custom EESS box made for 12v plus I’ve been looking the alternator part wouldn’t be that easy either. The starter would be easy as Power Master makes a 12v one for the civvy 6.5s and the IP solenoid would be really easy too.

Sound like your on your way to 12 Volts. $$$ Some of the OEM guys are going to blow a fuse at a project like this... and a small wad of money. LOL

12 volt controller...No problem. Don't go cutting start & glow circuits out just yet.

Guys got do their thing, CAMO

 

[TOBASH]

You need to rebuild the PCB with 12V solenoids using the schematics I posted months ago. You then need 12Volt starter. The Hummer starters are 1.2-2 grand each unless you go with a 12V gear reduction unit. You need a power inverter or a Jeep type windshield wiper and washer motor. You need a 12V flasher solenoid. Lights need conversion. Gauges need conversion. Engine block temp sensor needs conversion. Glow plugs need conversion.

Look at post 1 and 51 in the following thread for details on DIY PCB/EESS.

How to bypass PCB? I am aware some HMMWV owners have done it.

I'm not trying to speak sacrilege here, and I don't want to precipitate a war of words. :shock: How might I build a manual control box? My 24Volt Landcruiser just uses a glow wire to show glow plugs are ready, and then she just starts right up with the twist of a key. Civilian 6.2 Diesel...

www.steelsoldiers.com

 

[RayGunSlayer]

Well I’ve been doing some research on the alternator side of things and it looks like it’s going to be much easier for me to just keep my dual voltage alternator and only use the 12v off of the regulator in order to charge the battery. I would absolutely love to have a smaller alternator for more space in the engine bay but building a custom bracket and a wiring harness for a new alternator just doesn’t sound fun. If anyone has any ideas on a better solution for the alternator than please let me know. CAMO I will definitely be giving you a call here in the near future for a manually controlled 12 volt glow plug box!

 

[Milcommoguy]

Well I’ve been doing some research on the alternator side of things and it looks like it’s going to be much easier for me to just keep my dual voltage alternator and only use the 12v off of the regulator in order to charge the battery. I would absolutely love to have a smaller alternator for more space in the engine bay but building a custom bracket and a wiring harness for a new alternator just doesn’t sound fun. If anyone has any ideas on a better solution for the alternator than please let me know. CAMO I will definitely be giving you a call here in the near future for a manually controlled 12 volt glow plug box!

Welcome the call. If your going to go 12 volts, Go all the way. Could get good money for the 200 Amper to pay forward on the hardware. Have money left over?? Just a thought.

How many volts were used on Frankenstein? CAMO

 

[Mogman]

That 14V tap is only good for about 20A or so and I doubt very seriously it would work at all without the 28V tap connected to a set of batteries and as CAMO said go all in or not at all.
That 14V tap was only designed to compensate for the small ammout of 14V used by the transmission

 

[Autonomy_Lost]

Excuse my ignorance, but this seems like a lot of work to eliminate one battery. There are plenty of ways to run 12v accessories on the 24v system, I'm not really seeing the appeal of this conversion?

 

[Coug]

Excuse my ignorance, but this seems like a lot of work to eliminate one battery. There are plenty of ways to run 12v accessories on the 24v system, I'm not really seeing the appeal of this conversion?

I agree.
About the only thing I see is if there are plans to convert the motor to something else in the future.

 

[RayGunSlayer]

It’s not just about running other 12 volt accessories. It’s mostly about the cost of maintenance in the future. Like Tobash stated earlier, just a new 24 volt starter cost anywhere from $1,200-$2,000. If I convert everything over to 12 volts, the cost of all of it would be about the same in the long run just to replace the starter. Then when I sell off the old parts I’ll be in this conversion for not a dime except for my time.

 

[Sigi]

At 24V the wires are designed to carry half the current of a 12V system. That is the primary advantage of a 24V system. Converting a 24V system to 12V requires upgrading all high current carrying wires. After that is done, breakers and fuses will have to be upgraded. You'll probably still need two batteries in parallel to deliver the cranking amps at 12V. Not that straightforward.

 

[Milcommoguy]

At 24V the wires are designed to carry half the current of a 12V system. That is the primary advantage of a 24V system. Converting a 24V system to 12V requires upgrading all high current carrying wires. After that is done, breakers and fuses will have to be upgraded. You'll probably still need two batteries in parallel to deliver the cranking amps at 12V. Not that straightforward.

GOOD POINTS

YEP, You got that right IMO. There's more to it than just jump in and do it. Not so sure of any cost savings if proper maintenance, coupled with understanding of system is worth while $$$. Looks good on paper... till one pops the hood and really digs in. Most HMMWV wiring likely sized ok 14/12 ga. for most low current requirements. Battey to starter feeds (those fat wires) ok to, with some calculations.

In my case (who cares?) 60 Amp alternator, 100 Amp Cooper / Eaton Sure Power. Balances 12 volt battery buss and easily handles all of the 12 volt gear... a LOT of radios. A 12 Volt winch...might be a bad idea? Just don't get stuck and use radio to call for backup. LOL

https://www.eaton.com/nz/en-gb/catalog/emobility/series-21000-battery-equalizer-21060E00-21080E00-21100E00.html

Shop around for one. Better deals can be had NOS surplus.

On the surface doable. Good luck on this fun mod.

Been scratching my head on this thread too, CAMO

 

[RayGunSlayer]

Well truthfully I’ve been researching parts constantly and this seems pretty doable which means I’m gonna go through with it and see if I can make it work. CAMO, you seem very knowledgeable with wiring and electrical. One of the things I don’t understand is what I’m going to do with the AC tap wire. I’m planning on going with a high amp GM 3 wire alternator and don’t really know what to do with the AC tap wire. Any advice would be appreciated

 

[Mogman]

Unless it is driving a tachometer the AC tap is only used by the STE/ICE diag port, I have to agree with the others, it seems you are going to allot of expense and a ton of work so you could POSSIBLY save a little amount of money and work down the road, and lowering the resale value to boot.
But of course it is your truck to do with as you please.

 

[Milcommoguy]

Well truthfully I’ve been researching parts constantly and this seems pretty doable which means I’m gonna go through with it and see if I can make it work. CAMO, you seem very knowledgeable with wiring and electrical. One of the things I don’t understand is what I’m going to do with the AC tap wire. I’m planning on going with a high amp GM 3 wire alternator and don’t really know what to do with the AC tap wire. Any advice would be appreciated

DO nothing. You won't be using the not so smart box start box ??? so the AC signal is of no use. Not sure what alternator you are going with? Could just use that wire to get back to the dash and install an alternator fail idiot lamp.

Lots of work to save a buck, CAMO

 

[Milcommoguy]

Unless it is driving a tachometer the AC tap is only used by the STE/ICE diag port, I have to agree with the others, it seems you are going to allot of expense and a ton of work so you could POSSIBLY save a little amount of money and work down the road, and lowering the resale value to boot.
But of course it is your truck to do with as you please.

Monday morning quarter back .... AC tap only feed the controller. No connection to ICE-STE, not available there.

Heck of a job to tackle. With the RayGun all thing can be Slayed, CAMO Good Luck

 

[RayGunSlayer]

Awesome thank you for all the information! I’ll be sure to take that wire out of the wiring harness. Whenever I start ordering parts CAMO, I’ll be calling you for a new box!