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re-wiring M1031 & have a few questions

jesusgatos

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Adapting a 1966 Chevy cab to an M1031 chassis. Retaining 24V system, using the 1966 wiring harness for cab controls and instruments, and CUCV chassis/engine harness. Working on splicing the two harnesses together now, making some changes/upgrades at the same time. Slow going, but is coming together alright. Have a few questions though, and would appreciate some help.

Eliminating glowplug module, adding momentary button, and would like to replace stock glowplugs with 24V HMMWV glowplugs. Have read conflicting information about whether or not those are actually 24V though. Can anyone tell me for sure whether HMMWV glowplugs are 12 or 24V? Is that even possible, seeing as the glowplugs are grounded through the threads, and chassis ground is 12V?

Would also like to use the button-style glowplugs, ideally with 90-degree connectors if possible. AM General part number is 8338564, and nsn is 5940003996676. Looking those numbers up, appears they're just standard packard-style MS single wire connector. Are there any low-profile 90-degree connections for those available? Can't seem to find any.

Replacing stock glowplug and starter relays with a much heavier-duty pair of Stancor relays, rated for 200amp continuous duty. Found these while researching the doghead relays, and noticed that these also have isolated grounds, and are higher-rated. Also less expensive than the doghead relays, so maybe another good option?

Already pretty deep into the wiring, so decided to relocate the starter relay to the engine compartment. Think want to run one wire from +12v to one of the big lugs on the relay, and then another wire from the other big lug to the starter. Starter signal/switch wire goes to one of the smaller terminal lugs, and then purple wire goes from the other small terminal lugs to the small lug on the starter. Same question as glowplugs - how is the 24V starter grounded if the chassis ground is 12V and the 24V ground is floated? Obviously missing something.

Also removed the stock fuel filter setup and stripped out the ICE diagnostic stuff. Think was able to identify all the things knew wouldn't need for anything else, only wondering about the wires that went from the ICE to the alternators (brown wire and a black/white wire on the drivers-side alt, and a pink wire on the pass-side alt). Do those serve any other purpose, besides ICE? Planning on adding diesel tach using alt wire, would want to use any of those wires for that signal?

Will have more questions, but these are the most urgent things need to figure out. Thanks in advance for any assistance.
 
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Recovry4x4

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While I can't help with your questions, I'm interested in seeing how you mounted the cab.
 

jesusgatos

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Posted tons of pictures in the first link to the build thread on pirate4x4, but they blocked those links for some reason. Sucks, and this site won't let me upload pics from my phone. Sorry.
 
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Recovry4x4

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Posted tons of pictures in the first link to the build thread on pirate4x4, but they blocked those links for some reason. Sucks, and this site won't let me upload pics from my phone. Sorry.
Guess I missed the first link and probably better anyways. Pirate is an intolerable collection of folks that know everything except how much they don't know.
 

jesusgatos

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Meh, suit youself. Not much different in that way from most other online communities, including this place. For better or worse, this is the place for military specific stuff, and pirate is unrivaled for just about anything else offroad-related.
 

MarcusOReallyus

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Eliminating glowplug module,

Why? It's a much smarter system than any human operator.


adding momentary button,
Good backup to a stock controller card, but not a good replacement.


Can anyone tell me for sure whether HMMWV glowplugs are 12 or 24V? Is that even possible, seeing as the glowplugs are grounded through the threads, and chassis ground is 12V?
Ground is ground on these vehicles. (That's not always the case, but it is on these vehicles, so we can keep it simple here.) You could run 24v AND 12v AND 6v AND 48v all on the same chassis, same ground. No problem.


Replacing stock glowplug and starter relays with a much heavier-duty pair of Stancor relays, rated for 200amp continuous duty.

Again, why? You are only running about 80 amps to the GPs, less for 24v. The stock GP relay is plenty. The starter relay only draws about 9 amps. The stock relays seem to have a sticking problem (might just have been a certain run of them - nobody knows for sure), so the doghead is a wise mod, but even that is massive overkill. A standard 20 amp automotive relay would be fine, too. 200 amps? What for?

Same question as glowplugs - how is the 24V starter grounded if the chassis ground is 12V and the 24V ground is floated?
24v ground is NOT floated. 12v and 24v share the same ground. If you want to feed 24v to the GPs through a relay, you will have no problems at all if the relay is wired correctly.
 
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jesusgatos

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Why? It's a much smarter system than any human operator.

Good backup to a stock controller card, but not a good replacement.
Simplicity, eliminating quirky electromagical stuff.

Ground is ground on these vehicles. (That's not always the case, but it is on these vehicles, so we can keep it simple here.) You could run 24v AND 12v AND 6v AND 48v all on the same chassis, same ground. No problem.
Oh, excellent. Thanks for clarifying.

Again, why? You are only running about 80 amps to the GPs, less for 24v. The stock GP relay is plenty. The starter relay only draws about 9 amps. The stock relays seem to have a sticking problem (might just have been a certain run of them - nobody knows for sure), so the doghead is a wise mod, but even that is massive overkill. A standard 20 amp automotive relay would be fine, too. 200 amps? What for?
No reason except when went to buy doghead relays, saw these we're higher-spec and less expensive. Why not?

24v ground is NOT floated. 12v and 24v share the same ground. If you want to feed 24v to the GPs through a relay, you will have no problems at all if the relay is wired correctly.
Thanks Again, super helpful.
 

jesusgatos

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Harness connections are mostly made with wire nuts right now, so can verify everything is working right before making real connections. But would like to replace some of the lugs and fuse holders at the fuse block. Need to add a few circuits, re-route some wires, etc. Having a hard time figuring out what those items are called and whereto buy them though.
 

jesusgatos

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To clarify, will be adding second fuse panel, wired direct to power, triggered by relay. Just want to re-wire a few things in the factory fuse block to clean up the wiring for this custom application.
 

jesusgatos

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Oh, that's weird. When called to check prices and availability, local parts store wanted $60 for doghead relays and they had to order it. So went ahead and bought two of those for what thought was about the same price.
 
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