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Fusible Link; which one for my '78 BJ40?

Discussion in 'Diesel Tech and 24 volts Systems' started by bj40green, Oct 18, 2011.

  1. bj40green

    bj40green Tssss, tssss

    Messages:
    2,212
    Location:
    Playas del Coco, Costa Rica
    I’m the happy owner of a ’78 BJ40. Unfortunately a PO removed the Fusible Links from my harness so a few circuits are unprotected. I’m not happy with that situation. I want them back in the electrical circuit.
    I think I've read all the threads with the word "fusible" in it, but I can't find the the solution I'm looking for. I want the correct Fusible Links for my truck.

    My FSM wiring diagram shows 2 FL's. One for the glow plugs and one for the rest of the circuits. The EPC however tells me that there is only one with part# 90982-08025. Hmmmm:hmm:, That's problem number one.
    Are there two FL's with the same part#, or are those different and is there an error in the EPC?
    fusible link 1.jpg

    So I went to Pudy Motor (the official Toyota Importer) and asked if the FL is available. Answer...... No hay! which is Spanish for No Longer Available. Then I asked about the one or two in the EPC and FSM but now the guy looks at me if I'm the clown. As usual no help from Señor Toyota.

    At this point I'm confused :confused: both the FSM wiring diagram and the EPC gives no information about the FL's. What wire size, rating, value or whatever. I have the part# but that is not available. If it was available, is it for the glow plugs or the other circuits? Now what?

    I started a research to find out more about FL's. First about how they exactly work. (Thank you Google)
    ---- A Fusible Link is NOT A FUSE ----
    It's function is to protect the wiring (harness/circuits) in the truck from burning, melting, frying, whatever you want to call it by long time overload (excessive current draw) or a short (to ground).
    It doesn't burn out from a short time high current draw but from a long time high current draw before the wiring (harness) start melting.
    A Fusible Link is a piece of wire, 6 to 9 inches long with a special insulation which will not burn or melt. You can't see if it's defective or not. You can test it by pulling on both ends. If it stretches the wire inside is burnt.
    An AWG 10 wiring circuit is protected by an AWG 14 Fusible Link.
    The FL is always 4 AWG numbers higher then the circuit it protects.
    For more info on this click here -> Catalog

    Having this knowledge I ran into two new problems.
    1st. Toyota's are metric and have their wiring in mm² and not AWG.
    2nd. I still don't know what wire size the FL is that I need. The part number is telling me nothing.
    So I started looking at other wiring diagrams of BJ's and HJ's and found out that in the later years Toyota added a code next to each FL.
    fusible link 3.JPG
    I found (with the help of Lostmarbles/Tom) the following code's:
    0.3 P
    0.5 G
    0.85 R
    1.0 GR
    1.0 Y
    1.25 B
    2.0 L
    I suspected that the code was wire size in mm² and a letter for the color code. So 0.5 G means 0.5mm² Green, 0.85 R means 0.85mm² Red.
    Thanks to Mr Google I found the first part (the wire size) confirmed as you can see in this picture.
    fusible link 2 crop.jpg
    This table is from a supplier that sells Fusible Link wire by the meter. Unfortunately he used his own color code so there is no similarity with the Toyota color code's.

    If I set the color code aside i come to this table:
    Fusible Link..................Protects circuits with wire size
    mm²....AWG...................mm².....AWG
    0.3.......22....................0.85......18
    0.5.......20....................1.25......16
    0.85.....18....................2.0........14
    1.0.......17....................2.63......13
    1.25.....16....................3.0........12
    2.0.......14....................5.0........10
    3.0.......12....................8.36........8

    As you can see in the top picture in this page: Catalog a 2 sq. mm (AWG14) Fusible Link protects an AWG10 (5 sq. mm) circuit.

    Next step: I can only meassure diameters and not mm² !

    To be continued.......
    Last edited: Oct 22, 2011
  2. lostmarbles

    lostmarbles SILVER Star

    Messages:
    7,037
    Location:
    New Zealand
    Take another look Rudi.


    I see one 90982-08025 and one 90982-08101. (Note ...90982 rather than 90952 also.)

    :beer:

    PS. Great work.. You've really helped me here (as with everything else you delve into).
  3. bj40green

    bj40green Tssss, tssss

    Messages:
    2,212
    Location:
    Playas del Coco, Costa Rica
    I've looked Tom, in the GEN and in the Europe EPC but can only find 90982-08025 for my 02/78 BJ40. I can find 90982-08101 but that one is for 7901-8007.

    Anyway, I've studied the picture and think that it's a 2 in 1 Link.
    fusible link 6.JPG
    Which make sense but now the problem arises that (if I can find this FL) I have no clue which side is for what.
    So......................

    Rudi
  4. lostmarbles

    lostmarbles SILVER Star

    Messages:
    7,037
    Location:
    New Zealand
    I'll have another look at that 08101 when I get home tomorrow Rudi.

    I spent ages this morning looking at Toyota fusible link data and thought I'd almost stumbled on finding out the size specifications for those part numbers ... but alas it was not to be. (The people loading the information into the EPC gave specs for many other part numbers but not ours.)

    I think all one can do with our old 40series cruisers (when making up new fusible links) is:

    • match the wire by eye to the old link, or
    • Match it to the loom wire it is protecting by making it four AWG numerals smaller .

    :beer:
  5. bj40green

    bj40green Tssss, tssss

    Messages:
    2,212
    Location:
    Playas del Coco, Costa Rica
    As I don't have an old one to compare to I have to dig up the 2 wires in my loom later this week.
    BR (Black Red stripe) to the glow relay and W (White) to the starter relay and Amp gauge.
    The PO cut out the Fusible Links and replaced them both with Red wire :bang:.

    Rudi
    Last edited: Oct 20, 2011
  6. lostmarbles

    lostmarbles SILVER Star

    Messages:
    7,037
    Location:
    New Zealand
    Well I'm back home and I've confirmed for myself that you are indeed correct Rudi. (I wonder why I missed that! I guess I must have been rushing.).... So according to the EPC your BJ40 has 90982-08025 FUSIBLE LINK and mine has 90982-08101 FUSIBLE LINK.

    Yes. I believe Toyota should have used the term "FUSIBLE LINK ASSY" (where ASSY stands for ASSEMBLY) instead of just FUSIBLE LINK for our older cruisers.

    Here's a picture of a 3 in 1 40-series FUSIBLE LINK ASSY taken from this translated french site:Google Translate

    FusibleLink.jpg

    And here is my original 2 in 1 FUSIBLE LINK ASSY:
    FusibleLinks4.jpg

    On a pre-January 1979 BJ40 like yours I wouldn't expect to see the small wires for the external-shunt-style ammeter of course (because I believe that is the period that the ammeters changed to using one of the fusible links as an external shunt).

    :beer:
  7. bj40green

    bj40green Tssss, tssss

    Messages:
    2,212
    Location:
    Playas del Coco, Costa Rica
    Yes Tom, you're right. Sept. '77 till Dec. '78 has the full charge load running throug the firewall, throug the cluster, to the battery.

    Right now I'm sourcing the stuff I need to fabricate the links.
    I have a nice selection of heath shrinkable tubes, the connectors and the AWG wire. What Im looking for now is that special heath resistance tube to replace the standard insulation from the AWG wires. You'll find that (waxy, greasy, yellowish or black) protection tube in coffeemakers, deep fryers and other equipment that produces heath.
    It's the black piece of tube in your picture.
    The plan is to strip the plastic insulation from the AWG wire.
    Replace that with the heath shrinkable tube and cover that with the heath resistance tube.
    In the end it's gonna look like this:
    DSC06556.JPG

    Whish me luck in finding that heat tube.

    Rudi
    Last edited: May 7, 2013
  8. bj40green

    bj40green Tssss, tssss

    Messages:
    2,212
    Location:
    Playas del Coco, Costa Rica
    The birth of a fusible link

    I found the stuff I needed and had some time this weekend.
    So here is a picture of the birth of my first fusible link.
    On top is the solution from the PO when the FL(s) blew out.
    He twisted the White and the Black/Red together with a Red AWG 8 and soldered it (with a blow torch) together :bang:.
    No more fusible links, no more protection, thank you PO!
    fusible link 6.JPG
    The White and Black/Red wires are both 3mm Ø which is ± AWG 10.
    I took a piece of regular AWG 14, stripped the insulation and replaced that with white heat shrinkable tube, crimped and soldered the yellow male connector, added the heat protective tube and crimped and soldered the blue connector to it.
    The second (Red) one is shown in parts.
    Now I need some dry weather to install the stuff.

    Rudi
  9. lostmarbles

    lostmarbles SILVER Star

    Messages:
    7,037
    Location:
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    Very innovative Rudi :clap:

    I never thought of doing that.

    Instead I had to ask a friend in the USA to send me some fusible link wire (because I couldn't find any available in this part of the world and because I could find no overseas company willing to sell direct to someone in New Zealand).

    :beer:
    Last edited: Oct 23, 2011
  10. markthemenace

    markthemenace New Member

    Messages:
    428
    Location:
    Pitt Meadows BC
    Great work Rudi. There's a guy in the US that sells fusible links and seems very knowledgeable about them. I don't know him myself, but there are guys on the Samba forums that hold him in very high regard (I have a 74 bus too). Check out his website at: madelectrical.com

    All kinds of cool stuff ;)
  11. bj40green

    bj40green Tssss, tssss

    Messages:
    2,212
    Location:
    Playas del Coco, Costa Rica

  12. markthemenace

    markthemenace New Member

    Messages:
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    Location:
    Pitt Meadows BC
    Thanks Rudi...yeah, sure is! A lot depends on your google-fu though :)
  13. bj40green

    bj40green Tssss, tssss

    Messages:
    2,212
    Location:
    Playas del Coco, Costa Rica
    Finished this project today!

    Today i finished my little project and installed the two home made Fusible Links.
    Now that they are in I sleep a lot better. If anything goes wong the Fusible Link(s) should prevent a harness melt down.
    DSC06590.JPG

    Rudi
  14. lostmarbles

    lostmarbles SILVER Star

    Messages:
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    Location:
    New Zealand
    Nice job Rudi. :clap:

    I recently installed a fusible link in a wire I ran a long time ago off the big +Ve live lug on my starter motor. That wire is cable-tied to my clutch fluid line (between master and slave) and runs into the cab to an outlet that can supply accessories like a spot llight and a portable tyre-inflator air compressor (that I've since given away).

    Only after repairing my fusible links did I stop to think how Toyota had protected their loom wiring so well and how silly I had been. (I did have a 30A fuse in the line but that was quite a distance along the wire.)

    :cheers:
  15. bj40green

    bj40green Tssss, tssss

    Messages:
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    Location:
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    You're a lucky guy Tom. I assume that the 30Amp fuse was not mounted close to the starter B-lug but somewhere after the "cable-tied to my clutch fluid line" along the wire in the cabin?
    Imagine what would happen if that line got damaged by chafing or so.

    Cheers :beer:

    Rudi
  16. lostmarbles

    lostmarbles SILVER Star

    Messages:
    7,037
    Location:
    New Zealand
    At least I didn't choose a brake line Rudi. :D

    (I'm still not happy with following the clutch line ..even with the fusible link installed .... Trouble is, any other way would look so much more untidy.)

    :cheers:

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