HDJ81: 24v to 12v starter conversion

Discussion in 'Diesel Tech / 24 volts' started by TuffMudder, Jun 9, 2018.

  1. TuffMudder

    TuffMudder Still working on my FJ55!

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    I'm trying to convert from 24v starter to 12v using @FlyAddiction 's 1HDT 24v to 12v conversion step by step

    He says to connect the passengers side positive through the 5511e and a fuse to the aux fuse box. His diagram indicates its on the right hand side of the engine bay

    [​IMG]

    I'm trying to figure out where the auxillary fuse box is or if he's referring to the box's pictured below with wires going to the right side positive
    [​IMG]

    I've also encountered the cable in the pick below (ends in a ring terminal just above the top of the pic). I don't see it mentioned in his write up, but i'm also learning as i go
    [​IMG]

    Any help would be greatly appreciated

    Thanks
     
  2. AirheadNut

    AirheadNut

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    The box in your photo is the fusible link connection at the battery. I assume that the "aux fuse box" is the Auxiliary Power box located on the RH side of the engine bay next to the air filter housing. This is a rather poor photo, but the box is just visible:
    IMG_0418.jpg
     
  3. mudgudgeon

    mudgudgeon

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    The diagram above send very different from what you would find in a factory 12 volt HDJ80.
    The standard starting battery is on the left side of the engine bay, it's the one with the fuseable links.

    Do you have the factory electrical wiring diagrams?
     
  4. TuffMudder

    TuffMudder Still working on my FJ55!

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    well, now i now why i've had trouble. I had a new airbox put in and the fuse box mustve been moved. where to is the question. The airbox is a pita to move, but i checked under it yesterday and didn't see it. This will be a huge help though. At least i know im in the right location
     
  5. TuffMudder

    TuffMudder Still working on my FJ55!

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    it was relocated inside the fender :(

    Time to research how to remove the fender
     
  6. FlyAddiction

    FlyAddiction

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    I will take more pictures of the box in question and upload them as soon as I can.
     
  7. TuffMudder

    TuffMudder Still working on my FJ55!

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    Thank you.

    I've been slowly chipping away at it since each step is new to me. Once i took the fender off, I finally found the power box for the house neg and main pos so i'll be able to complete that part which will just about finish it. everything makes sense, but i did have two positives to bring over from the passengers side. One you discussed in your right up and the other came from under the batter box and is pictured above. Not knowing what that is bugs me, but it seems to be a positive, so i just ran it over to the drivers side main with everything else

    I also didn't have space on the drivers side for the 5511e so i put it on the passengers side which makes my wiring a bit more cluttered but still workable
     
  8. carbon60

    carbon60 SILVER Star

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    Why the change to 12v?
     
  9. TuffMudder

    TuffMudder Still working on my FJ55!

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    I experienced the pitfall of a 24v system and the decision was easy

    My understanding is the advantage of the 24v starter is easy starting in sub-zero weather. In Fort Smith, AR we can go back to back years without seeing snow and 20 degrees sunny and clear will shut the entire town down.

    The disadvantage of the 24v system is, if there is a drain on the system it pulls both batteries down equally and then it takes a 2 car jump start which proved suprisingly difficult as apparently no once carries jumper cables any more. I tried a single jump and even a single jump with a battery charger on the second battery without success.

    Since i don't foresee a need for the 24v starter and prefer the advantages of an isolated auxillary battery, the decision seemed easy for me
     
  10. TuffMudder

    TuffMudder Still working on my FJ55!

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    I have the electrical diagrams but they didn't help me much. For instance, i wasn't able to find the B positive junction box on it and i knew exactly where it was. That being said, the only FSM i was able to find was for the HDJ80, i assumed that was the same. I found it with google, because every link in the forums is broken.

    As to the above being different, in his step by step post, Flyaddiction mentioned that he went with left side for the starter so that he didn't have to move the fusible links

    By the way, somehow i missed your post originally @mudgudgeon and just saw it today reviewing this thread
     
  11. AirheadNut

    AirheadNut

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    The wiring diagrams for an HDJ80 will be very different from those for an HDJ81, as the 81 had 24V starting and the 80 didn't.
     
  12. TuffMudder

    TuffMudder Still working on my FJ55!

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    That's unfortunate as i still haven't found the hdj81 specific manual. I'll take another look
     
  13. mudgudgeon

    mudgudgeon

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    @TuffMudder
    The FSM wiring diagrams are generic, they show 12 & 24 volt start for HDJ80/81
    and non standard options
     
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  14. mudgudgeon

    mudgudgeon

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  15. TuffMudder

    TuffMudder Still working on my FJ55!

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    Thanks @mudgudgeon. That is actually the one I mentioned above that Ive already downloaded (all 1000 pages), and it does have the wiring diagrams in it.

    i did have problems using the wiring diagrams. I was trying to find B+ junction box to see what had previously attached to it, but wasn't successful. I assume its just my general lack of familiarity and will continue trying to use the diagrams. The rest of the manual of course appears to be pure gold...well, except where they decided not to include how to remove the fenders. Fortunately a quick google search resolved that issue.
     
  16. TuffMudder

    TuffMudder Still working on my FJ55!

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    I spoke too soon @mudgudgeon . The ewd's i had looked at included some diagrams of the engine bay, but was primarily for the body wiring which would explain why i couldn't find what i needed. Sending you a pm about your diagrams
     
  17. carbon60

    carbon60 SILVER Star

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    Makes sense to me, for sure. I've not yet had a need to jump my rig, and it was below -30ºC for a week, last winter.

    I was contemplating getting a pair of LiPo booster packs…
     
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  18. mudgudgeon

    mudgudgeon

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  19. TuffMudder

    TuffMudder Still working on my FJ55!

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    10 days since I started on the conversion to a 12 v starter. I'm pretty sure im in the running for the record for longest swap in what others have said was a one day project.

    I believe i have everything hooked up correctly and i have rechecked everything at least 4 times. It was late when i finished so i'll try to start it tomorrow but wanted to post how its set up in case anyone had any comments before i risk an electrical fire in my LC tomorrow.

    The wiring is currently set up with:
    1. 12v starter going to the 5511e battery switch then to main battery (+)
    2. The main battery (+) going to a 150a fuse then to the Battery Doctor 150a battery isolator and then on to the Auxillary battery (+). Battery doctor is grounded to the body
    3. Main battery (-) is grounded to the body, engine block and the Auxillary Power box
    4. Aux battery is grounded to body and engine block
    5. Alternator to Aux battery (+)
    6. Aux battery (+) goes to 5511e and returns from 5511e to a 150a fuse and then on to +B terminal in the Auxillary fuse box.
    7. Aux power box (-) to Main battery (=)
     
  20. FlyAddiction

    FlyAddiction

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    Mudder,
    Sorry about the late repply. I have been extremely buisy with a newborn on the way. In the 3rd point of your last post you list:
    "Main battery (-) is grounded to the body, engine block and the Auxillary Power box"
    I did not ground the main(starter) to my auxiliary fuse box but i did connect the aux - to it. Below you will find a pictures of what i connected to the main(starter) +. The first picture shows what was already connected to the passenger side battery + and the second picture shows the little box that was connected to the drivers side + that i extended to the main +.
    Hope that helps

    20180617_062701.jpg

    20180617_062745.jpg
     
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