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Thread: HMMWV 100/200 amp alternator on stock engine

  1. #1
    Join Date
    Jun 2020
    Location
    washington 98620 usa
    Posts
    46

    Default HMMWV 100/200 amp alternator on stock engine

    Incase anyone has ever wondered what other alternator can fit in our truck with the 230 engine, i managed to get my hands on a used HMMWV alternator for about the same price as a 60 amp alternator. It does take some semi minor modifications to fit. This particular one is a 200 amp and is a bit to much for the batteries, but the 100 amp is exactly the same size. What is needed for the modification to fit is a different upper alternator bracket and a 1/16" spacer to sit behind the pulley. Im not sure what universal upper alt mount to use but i used one that came off my old cj with a 232, and a 0 AWG 70" cable. My batteries were installed horribly in the passenger fender so for an oem location batteries you'll need to measure. But cable came from an HMMWV also and was $20 new on ebay and i only needed to shorten it about a foot. You will need a three band pully, but will only use two of the bands. You will also need two new belts that are about 1.5" longer. It does clear the hood mounted air filter if you have one. I tied in the original hookups for the electrical system. I may later go in and put in a fuse at about 60-70amps for further protection but havent yet. Seems to be fine so far.

    Edit for the post: The alternator i used is NSN #:2920-01-420-9968, Part #:12447109. This is the 200 amp version. The 100 amp version is NSN #:2920-01-407-0532, Part #:12447110, N1505-1. This version is alot better for our trucks. The 80" cable I used is NSN #:6150-01-416-7899, this cables is prebuilt and 0 AWG. There is a 100" cable but i do not have a part number for it. But they both come off first and second gen HMMWV m998. Both these alternators are the same size and similar weight. Most of the specs and stuff i have to say will be based off of the 200 amp alt because thats what i have. You are able to find used alternators for about the same price as a new 60 amp. I personally would not recommend this alternator set up if you do not have alot load use requirements or if you can not find one reasonable priced. The Average Used price for one is about $1000 and a brand new one is about $2500, so it wpuld be worth passing on for price alone. I spent $450+ $150 shipping for mine. The 60 amp alternator is about 8.5" across from upper mount to lower mount hole, the 100/200 is 10". If you get a 100 amp alternator you may not need to get a 0 AWG cable. The cool part about these alternators is that they are 24v/14v output. The HMMWV sometimes came with an alternator that had 12v sensors and solenoids in them and would drain the batteries unequally resulting in premature battery failure in one of the batteries. To fix this they would drag a battery cable from the 14v side of the alternator and attach it to a 12v positive bus bar to provide constant 12v power to the battery to keep them eventually charged. I am planning to do the same. I hope to have a decent amount of fun electronics to keep me entertained and comfortable. Both 12v and 24v. If you do decide to use this alternator but not utilize the 14v side then you will need to drag a jumper wire from it to the negative post to create a designed "short" then to cause the regulator to ignore it. I'll keep this post updated as i go about my day to day.
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    Last edited by Dreadwater; April 30th, 2024 at 12:12 AM.

  2. #2
    Join Date
    Nov 2009
    Location
    Greenwood, Indiana
    Posts
    1,705

    Default

    Good info
    Thanks, George
    Joshua 24:15

  3. #3
    Join Date
    Sep 1998
    Location
    North Central Wisconsin
    Posts
    11,532

    Default

    Great info and thanks also for the pic...this is very good news!!
    Lord send your Holy Ghost into our hearts and make the desire of our hearts Your Will.

    Pro-choice, that's a LIE, babies don't choose to die!!

  4. #4
    Join Date
    Jun 2020
    Location
    washington 98620 usa
    Posts
    46

    Default

    I'll keep yall updated on road test and what not. I'll also sit down and throughly record everything i did.

  5. #5
    Join Date
    Sep 1998
    Location
    North Central Wisconsin
    Posts
    11,532

    Default

    Love to make a tech page for this!
    Lord send your Holy Ghost into our hearts and make the desire of our hearts Your Will.

    Pro-choice, that's a LIE, babies don't choose to die!!

  6. #6

    Default

    Love it when stuff like this gets posted. Great solution and it looks like a super clean install.
    Liz, covid, murdered 10/19/21

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