Making Fusible Links

[TomoHawk]

In stead of ordering fusible links from an eBay seller, or from a mail-order retailer, both of which are getting harder to find and may soon be no longer available at all, I think I can get the correct wire from local Auto Parts stores.

I have not had an opportunity to dissect one to see how it's made, so I'm asking if anyone has looked into this. It looks like a fusible link is just a short segment of insulated wire with a female blade-connector crimped to the ends, but the OE ones look like the connector pierces the insulation to make contact with the wire inside.

After I get some replacements installed, I will take apart one of the old ones to see how you could make one yourself.

[Mikes Z car]

I thought I looked at how the links are made and there was insulation made of fiberglass (in addition to the wire insulation?) with the idea that it won't melt at high temperature keeping any melting metal from a burning out link from falling on anything and starting a fire. Then there was the idea that the link is one gauge smaller than the wire it was protecting, but maybe a non standard smaller gauge? It might be that the insulation is pierced to insure that all of copper conductor part of the link is fully encapsulated with the fiberglass insulation. If you take one apart please post pictures I am curious about how they make the links. I wonder if a caliper could be used to verify the gauge of the link wire though that might be tricky if the link is stranded, don't know.

[TomoHawk]

Ah, the enigma off the fusible link.

I'm going to cut up the old fusible link later on, but I agree that it's most likely not a normal type of electrical conductor. First off, it's very flexible, like a piece of lead solder, which does melt at a specific temperature. It needs to be insulated from engine heat, and tolerant to the the heat generated from flowing electronic current. It also needs to be contained once melted, and the outer jacket may even be charred, depending on the circumstances of the overload.

I just received a set of new fusible fuse links (three brown and 1 black) and they are all of a noticeably smaller gauge, especially the brown one. BTW- I got them through eBay from "z-connexion" who has a good reputation for parts, IMO. I suppose, because of modern technological advances in metal alloys, fusible links are now made of a smaller gauge?

[Mikes Z car]

They are supposed to be 4 AWG sizes smaller than the wire they protect per Wikipedia at

https://en.wikipedia.org/wiki/Fusible_link

An electrical fusible link is a type of electrical fuse that is constructed simply with a short piece of wire typically four American wire gauge sizes smaller than the wire that is being protected. For example, an AWG 16 fusible link might be used to protect AWG 12 wiring. Electrical fusible links are common in high-current automotive applications. The wire in an electrical fusible link is encased in high-temperature fire-resistant insulation to reduce hazards when the wire melts.

I wonder if the wire you have is flexible because it is a smaller gauge or because it is made out of some alloy?

[Zed Head]

I suppose, because of modern technological advances in metal alloys, fusible links are now made of a smaller gauge?

Probably just the insulation.

[beermanpete]

The wire used is ordinary copper wire coated with silicone insulation. Like any fuse, it needs to have a smaller cross-sectional area to ensure it melts before the circuit it protects, hence the 4 wire gauges smaller rule of thumb. The silicone insulation is used so it does not burn and cause a fire. As a result, the fusible link can open (do its job) without damaging the insulation which is why they are sometimes overlooked when troubleshooting a no-power condition.

[TomoHawk]

I remember reading some old literature that said the fuse link would look charred if it had melted (BTW- the melting point of copper is 2000! degrees F) but modern parts are different, obviously.

[Mikes Z car]

Tomo,

One thing I read yesterday is that you can pull on the ends of a burned out fusible link and it will stretch like a rubber band.

beermanpete,

Thank you for the information.

[TomoHawk]

That's probably right, if if the insulation is really made of a silicone material.

Anyway-

I dissected the severed fusible link for the headlamps (it's a brown one) and took a few photos.

I noticed that some of the copper strands were melted together, as if you tinned them with solder. The rest of the strands were corroded black, in the usual way.

NOTE: You should probably install new fusible links, to provide proper protection from overloads. Old ones aren't up to the standard.

The conductive part was certainly not very substantial, and it looks like the new fusible link I just got has the same size conductor, but with a slightly thinner outer jacket.

I think we can finally say that a fusible link is not "just like" a fuse, as some people who install MaxiFuses think. Neither can you say that there is an equivalent amperage. As Beermanpete stated, it's simply a smaller gauge conductor, and if you wish, you could make your own fusible link, with out any "voodoo" science involved, and that it is perfectly safe to use a piece of WIRE in place of the fusible link, as long as it's the correct gauge of wire.

Edited May 16, 2014 by TomoHawk

[TomoHawk]

So now I'm off to the dollar-store to see if I can find a plastic tube suitable for holding my spare fusible links. Incense or pipe leaner containers come to mind. I think I'll do that tomorrow, since it's next to the coffee shop.

[madkaw]

I guess I would wonder why anyone would take the effort and time to deal with fusable links unless you were stuck on Only doing Oem .

Time and effort to do an updated fused link of some kind that doesn't leave you guessing - what's in the wire?

Just IMHO

[Mikes Z car]

What I read is that a fusible link can briefly withstand a greater short circuit than a fuse can. If true then a maxi fuse might blow prematurely compared to the protection offered by a fusible link. But, new cars don't use fusible links, they use fuses right? My own car (240Z) has a hard to find large glass cylinder 40A fuse in place of the fusible link, no problem so far but I have had no short circuits. If my battery goes dead and the 60A alternator in the car tries to push 60A charge current through that 40A fuse I might be looking to find a replacement fuse. I would want to keep melting wire from a fusible link burning out off of anything but what material would offer that high temperature protection that you could buy? A fiberglass sleeve? Cooper makes fusible links that are a tin alloy and another kind that is a silver alloy but I didn't see any indication they use them in automotive applications, just in load centers.

Edited May 16, 2014 by Mikes Z car