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jstck 05-23-2019 01:11 PM

I posted this question in the Electrics/wiring thread, but I'll try here as this thread seems at least as relevant.

I have burned the fusible link in my 1990 D21 (which originally had a carbureted Z24). It looks like some of the earlier posted pictures, with a single female spade connector in one end (at battery), and two male ones connecting to the wiring harness, both with plastic housings. It has one black and one blue cable on it, and I blew the blue one (black is still intact). Some pictures of 24022-01G00 look just like it.

The short was caused at the ignition key, where +12V was shorted to ground when a cable came loose. That has been fixed and secured better, so I'm good there. However, I am unable to find the correct fusible link locally (Sweden), Nissan says they don't have any, and shipping from abroad gets relatively expensive for a small simple part like that.

I'm perfectly willing to replace fusible links with regular fuses though, wiring wise it's pretty straightforward and not my first rodeo. I know people say "they're not the same thing" (and they are not quite), but with the proper fuse rating it will do the job well enough in protecting cabling from short circuits and keeping my truck from not being on fire.

I have never found a wiring diagram that matches my truck completely (it's an anachronistic very late carbed Z24 due to Sweden being later with emissions restrictions) and some things seem to be just "different". So, while I'm unable to tell exactly which power cable goes where from the fusible link, the blue one leading to the ignition key +12V would match observations. Nowhere are there any current ratings for the fusible link though.

Right now I just jury-rigged the fusible link by replacing the blue wire with a 30A fuse just to be able to move it, as it just seemed reasonable given the wire sizes and what it appeared to be powering (and it starts and runs and hasn't blown yet). If I can't acquire a new fusible link I want to replace it with fuses, probably the bolt-in "midi" kind. What rating should I have for such fuses? Judging from the diameter of the fusible links, it seems like the blue one could be similar enough to a 20-30A fuse, and the black one maybe 40-50A, but I'd like to have a guess that is a bit more qualified than that.

If it comes to that, I'll just stick the fusible link in line with a smaller fuse, short a starter battery, increase the fuse current rating until the fusible link wire blows before the fuse, and pick the largest fuse below that. Almost like science.

jp2code 05-23-2019 01:45 PM

The short answer from me is, I think the fusible links are color coded. So if you can find fusible link wire of the same color, it should have the same ratings as the fusible link wire you burned out. I'm not 100% on that though.

jstck 05-24-2019 06:16 AM

Yeah, I've seen a couple web pages suggesting that, and the thickness seems it might match those listed (blue is said to be 0.8mm^2 / 18aw, black 1.0mm^2 / 16awg). There are however a few different colours used for the same Nissan spare part which makes me think they maybe just abandoned that colour-coding scheme later or something. Even then, there are no current ratings anywhere, just "use this fusible link wire for that other wiring".

ahardb0dy 05-24-2019 01:44 PM

are there any junkyards around you? Possibly could get one from another Nissan. I'm sure different cars used the same part.

jstck 05-25-2019 05:47 AM

There are precious few "pick-and-pull" junkyards still around in Sweden, and the D21 is not a very common vehicle. There are junkyard parts available for it, but there's a certain set of parts all the junkyards decide to keep and the fusible link isn't one of those.
I could go look for other random Nissans, but there is very little of similar age around anymore. It seems Nissan, like pretty much everyone else, switched to the "big fuse-looking plastic unit" style shortly after.

I'll keep looking, and maybe try some other Nissan dealers (I suspect my local one is particularly useless) or possibly have a friend in the US buy one and mail it to me. The truck hasn't blown the fuse I put in nor caught fire yet, so it may not be that urgent.

I am still however considering just replacing the fusible links with regular slow-blow fuses. I already have an extra fuse wired straight from the battery to power all the things I added when I swapped the engine and could just build something a bit nicer-looking with 3-4 big fuses (replacing the two fusible links + the "new stuff main fuse" + maybe one for future expansion). I just like having something that is totally under my control when it comes to maintaining it, and even if it won't have the exact same characteristics as the fusible links, I'll settle for "close enough".

PoodlePuncher 03-31-2020 03:37 PM

Chiming in, because in all the fusible link threads, i haven't seen it mentioned.

Fusible links are regular wire, just 4 or 5 gauges smaller than the wires they are protecting, because the smaller wire will burn up before the larger one.

Other than following an established color code, what makes "fusible wire" special is that the outer coating will not catch fire.

While it is possible to buy rolls of the "proper" stuff... for our application, it's not really feasible to make your own, unless you also have the correct terminals to crimp on the ends.

not to mention the proper (i.e. expensive) crimper for that specific terminal.

i learned all about this topic, back in the day, thanks to my 82 RX7. it was down for almost a year, because i couldn't find the "special wire" that i needed.

turned out, the easily sourced fusible link cartridges fit in place of the wire loop.

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