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Thread: How to: Replace fuse block

  1. #1
    My friends think I'm nuts jawn101's Avatar
    Join Date:  May 2011

    Location:  Sacramento-ish

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    How to: Replace fuse block

    We all know our fuse blocks need replacing. It looks like a daunting task - and it's not easy, but it is very doable with some basic tools and knowledge and a lot of patience.

    What you'll need:

    - Depending on your skill and familiarity with the tools and procedures used here, quite a few hours. I am a pretty experienced solderer and this took me about 10-12 hours total because of the cramped workspace and the fact that I was more or less flying blind and wanted everything perfect.
    - Soldering iron and solder
    - *Proper* barrel crimping tool - don't cheap out on this. You'll only end up with bad connections which you'll regret. I bought this one and it was great. http://www.amazon.com/gp/product/B003MWJ6SA
    - Electrical tape
    - Heat shrink tubing and a lighter
    - Pair of wire cutters/strippers
    - A sharpie that will be visible on the tape you have. If you have black tape, a silver sharpie is great. If you have a lighter color tape, black will work.
    - A head-mounted LED lamp
    - A bucket or milk crate or something low to sit on in the car
    - Small screwdrivers or picks to remove the old terminals from the old block
    - Fire extinguisher
    - Beer

    Here's my old, melted fuse block before I started.
    IMG_0666.JPG

    And here's the nice new DMCH one I put in. The process is much the same if you get a block from another vendor, but they may not fit as perfectly in the compartment.
    IMG_0765.JPG

    Take out your passenger seat and set it aside.
    IMG_0705.JPG

    Disconnect your battery. No fooling around on this step for this job.

    Remove the back shelf carpet, and the cover from the fuse/relay compartment and set them aside. You won't be needing them for a while.

    Pull all the fuses from the block, and all the relays from their sockets. Be sure you record what goes where if your relays aren't clearly marked as to what's what. Most are interchangeable, but not the red, green, white, blue (shame on you!) or Lambda modules.

    Detach the fuse block from the clips holding it down. These just snap in from the underside, so if you gently pry the block up, it will come loose. Here's a photo of the underside of the block.
    IMG_0769.JPG

    You may now want to unscrew the relay strips from the front and back of the electrical compartment. This will give you a little more slack in some of the tightly bundled wires when you have to cut them back. Now is a great time to replace your fan fail jumper, since it can be hard to get to in that corner when everything is screwed down. Drink a beer.

    Photos of the relay strips when removed:
    IMG_0767.JPG

    IMG_0766.JPG

    Look at the underside of the fuse block. You'll see all the wire pairs are just "clicked" into place from the underside. You'll use your small screwdriver to pop them out - either pushing from the fuse side, or prying from the underside. Whatever's easier for the specific pair you're working on (it will vary based on what position it is in the block, which wires are still in place, how taut the wires are, etc)

    IMG_0768.JPG

    As you pull out each pair, wrap it in electrical tape and number it carefully with your sharpie. I also kept a running list on a notepad of which color wire was on the left vs the right because I'm really anal. Be sure you let the ink on those tape wraps dry thoroughly - when I did mine I was sweating all over the place and smudged more than a couple of these, which made identification later a little harder. Drink a beer.

    IMG_0770.JPG

    IMG_0771.JPG

    If any of the terminals won't come out of the block due to warping/melting, don't be afraid to just clip them - just do it as close as you can to the block, since you probably don't have a lot of extra wire to play with.

    If it's going to be your first time using the barrel crimping tool, this is a good time to familiarize yourself with it extensively. They crimp somewhat differently than just smashing a butt connector with a pair of pliers, and you should have a good feel for what it's going to do. I had more than one failure to crimp perfectly, which let the wire slide back out after the terminal was smushed. DMCH includes a few extra terminals with your fuse block, but not many - so practice, but leave at least a couple spares in case you make a mistake. Drink a beer.

    Note! Be sure not to let too much metal debris fall into the electrical compartment. This means clipped-off terminals, small bits of broken wire, any dust you create when sanding the wire, etc.

    Once you have all of the pairs removed and labeled and know how to use your crimper, it's time to put the new terminals on. Do this one pair at a time, starting from one corner (your mileage may vary on which one's better to choose, depending on the condition of your wires, how they are taped, how taut they are, etc) and working in vertical columns. Unwrap the pair of wires you want to install. Clip the old terminal off, as close as you can to the end of the wire. Strip back about 1/4" of insulation and check the condition of the wire. If it's corroded, you will want to sand it lightly with some fine grit sandpaper. Slip a small bit of heat shrink tubing over the wire and push it down, away from the terminal. You don't want it to shrink up while you're soldering. Insert the wire into the barrel end of the terminal and crimp it down tightly. Tug on it to be sure the connection is tight. Apply a small amount of solder to the barrel end, being sure that it flows into the strands of the wire. Let the joint cool and then bring the heat shrink tubing up over it, then heat it up. Repeat this for the other wire in the pair, then snap the terminals into the fuse block. Note that some of the wires are doubled up inside the terminal. You just have to be extra careful that they don't slip out while you crimp. Drink a beer.

    BE CAREFUL! Once those terminals are in the block, you are going to have a very difficult or impossible time removing them again without damaging the terminal. Ensure your connections are good and tight and that you are putting things in the right place, or at least that you still have some extra terminals

    Once you've re-crimped and soldered all of the terminals, and clipped them back into the block, you're almost done! Clean up any wires that need to be re-wrapped or re-routed. Clip the fuse block back onto the bracket. Screw the relay strips back to the compartment walls. Reinstall your relays - be careful to put them in the correct spots! Also be careful that you don't just push any of your terminals out the bottom of the relay blocks when reinstalling the relays - it can happen pretty easily. Be sure the relay tabs are actually making connection with all their connectors. Install your fuses back into the fuse block. Be sure to use the correct amperage. Reconnect your battery, being sure that your fire extinguisher is standing by. Test everything!!
    IMG_0779.JPG

    If you've done everything correctly, you now have a beautiful new fuse block that isn't melted and shouldn't melt in the foreseeable future!
    IMG_0783.JPG

    Congratulations! Drink two beers.
    IMG_0785.JPG


    Hope this is helpful to those of you who still need to do this.
    Jon
    Last edited by jawn101; 08-04-2011 at 05:22 PM.

  2. #2
    Senior Member Bitsyncmaster's Avatar
    Join Date:  May 2011

    Location:  Leonardtown, MD

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    Here are a few more tips doing the install.

    1) If your going to use heat shrink tubing, cut up the tubing to length before you start. That leave one less thing to do on your knees in the car.

    2) Before you start, Look at the fuse block in good light and point a flash light in one side and look in the other. I found a few fuse pins hard to push in and that was due to some plastic flashing that remained after the blocks were molded. Much easier to do this on the kitchen table than in the car. Remove flashing with exacto knife

    3) The wires I stripped back to crimp would have soldered OK without sanding them shinny. So as long as your solder has a mild flux in it, you can solder without sanding.

    4) Use an extra pad for your knees to increase your work time.

    5) Before you push in a pin, make sure the wire is not tangled in the bundle. So pull the wires so they are grouped and don't look tangled up.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  3. #3
    Member
    Join Date:  May 2011

    Location:  Hickory, NC

    Posts:    32

    Will this crimp tool work as well?

    http://www.amazon.com/JT-Products-50...0532643&sr=8-4

  4. #4
    My friends think I'm nuts jawn101's Avatar
    Join Date:  May 2011

    Location:  Sacramento-ish

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    Club(s):   (NCDMC) (DCUK)

    Quote Originally Posted by hollywood2311 View Post
    Looks like exactly the same tool to me, but more expensive..
    Jon
    1981 DMC-12 #02100. July 1981. 5-speed, black, grooved w/flap.
    restoration log, April 2012 to present
    restoration log, March 2011 to April 2012
    full and detailed photo restoration log

  5. #5
    Member
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    Location:  Hickory, NC

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    But I have a friend who has Amazon Prime, so free 2 day shipping

  6. #6
    My friends think I'm nuts jawn101's Avatar
    Join Date:  May 2011

    Location:  Sacramento-ish

    Posts:    4,247

    My VIN:    02100

    Club(s):   (NCDMC) (DCUK)

    Quote Originally Posted by hollywood2311 View Post
    But I have a friend who has Amazon Prime, so free 2 day shipping
    Still more, but OK Either one works.
    Jon
    1981 DMC-12 #02100. July 1981. 5-speed, black, grooved w/flap.
    restoration log, April 2012 to present
    restoration log, March 2011 to April 2012
    full and detailed photo restoration log

  7. #7
    Member
    Join Date:  May 2011

    Location:  Hickory, NC

    Posts:    32

    BTW, fantastic write-up here. Almost done with replacing the block on 1776.

  8. #8
    My friends think I'm nuts jawn101's Avatar
    Join Date:  May 2011

    Location:  Sacramento-ish

    Posts:    4,247

    My VIN:    02100

    Club(s):   (NCDMC) (DCUK)

    Awesome. Keep at it, it takes time and patience but is worth the effort. You do have beer and a fire extinguisher nearby, right?

    Come to think of it, eliminating one greatly reduces the risk of needing the other... lol
    Jon
    1981 DMC-12 #02100. July 1981. 5-speed, black, grooved w/flap.
    restoration log, April 2012 to present
    restoration log, March 2011 to April 2012
    full and detailed photo restoration log

  9. #9
    Herbert Gibbs herbertgibbs's Avatar
    Join Date:  Nov 2012

    Location:  Hazel Park

    Posts:    2

    I wanted to replace my fuse block i am glad you shard these tips. These proved very useful to me.

  10. #10
    10515 dtavres's Avatar
    Join Date:  Nov 2015

    Location:  Orange, CA

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    Club(s):   (PNDC)

    Unhappy

    #7 just melted in my block

    I'm going to blame myself for not tucking the block cover away neatly. I was told by DMC to just take the cover off, as the block get hot, and there's no reason to keep the plastic cover on. But... I only laid it 'on top' of the other wires there, and apparently when I put the wood back down, the cover was pushing against #7. I'm guessing the heat build-up caused it to fry Dang it. My own stupidity. UNLESS, there's some other reason this happened? Anyone?

    DSC02473 (Medium).jpgDSC02475 (Medium).jpgDSC02478 (Medium).jpg
    Dave Tavres | #10515 | Orange, CA | Southern California | www.DMC10515.com |

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