Question On Fusible Links

So I tried starting my car this morning and nothing. Found the fusible link was melted through. OK have a spare and replaced all is fine.

Now, why? Why would this thing melt?
I'm running two electric fans. One 10" for the condenser and a 16" for the radiator. I have a very great A/C. I have a 75 amp. alt and a Optima Yellow Top battery.

It's been running like a top up to this point. Anyone have any ideas on why the link melted?

BTW, if this link melts where do I get another? I got my spare from EBAY. Or can I make one?

Thanks guys.

Electricity is still a mystery to me. lol.

Fusible links are really undersize wire meant to act like a fuse. In a 37 year old truck, they can just fail from old age. The manual can tell you what the fusible link is rated for - then you can make a new cable with an inline fuse of the size the link was rated to replace it.

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Originally Posted by pennyman1

Fusible links are really undersize wire meant to act like a fuse. In a 37 year old truck, they can just fail from old age. The manual can tell you what the fusible link is rated for - then you can make a new cable with an inline fuse of the size the link was rated to replace it.

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Roger. Thanks for that reply.

Corrosion from moisture + age + extra load = POP. The higher amp alternator and add ons to the electrical system will expose all the weak points in the wiring and fuses. The electricals in these trucks are rudimentary at best to start off with.

Also a bad ground and corrosion in the bat cable will cause them to pop.

https://www.youtube.com/watch?v=2ytPnSAn-3E

My fusable link box went bad. Bought a fuse box to replace it.

https://www.amazon.com/GXG-1987-Blad...ade+fuse+block

Quote:

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Originally Posted by pennyman1

Fusible links are really undersize wire meant to act like a fuse. In a 37 year old truck, they can just fail from old age. The manual can tell you what the fusible link is rated for - then you can make a new cable with an inline fuse of the size the link was rated to replace it.

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Yeah, probably just old brittle wire that finally had it. From everything I read when re-wiring my truck a fusible link is just one or two gauges smaller from the actual wire size that it's connected to, and like said it just acts as a fuse so too much current can't run through the wiring.

Quote:

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Originally Posted by camoit

Also a bad ground and corrosion in the bat cable will cause them to pop.

https://www.youtube.com/watch?v=2ytPnSAn-3E

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Thank you. But if you buy an Optima or any completely sealed battery you will never have a problem with corrosion, at least not from the battery.

A quick note. The manual states .5mm which equates to a 20 gauge fusible link.
I got it running. I soldered the old connectors and used the stock snap clips. I am running 18 gauge for now cause it's all I could find. When the 20 gauge wire come in I'll make another and use the 18 as a spare.
I changed out my alternator back to the stock output. Removed one electric fan. Was running two. And relocated the signal wire
to the fan. So far so good.

Are you running the fans with a relay taking power directly from the battery? That way it does not fry the fusible links. A higher output alternator won't fry the link either - put it back on.

When it comes to the charging system, you can't go wrong with the phrase "bigger is better". A higher CCA rated battery and amperage alternator will help the starter motor crank over with less effort and you won't have you headlights dim when you have everything going (you know, when the weather is crap and it's freezing) If you have decent alternator running the show, are you going to uprate your headlights to H4 halogens? I've got my eye on a full set and harness adapters to run relays off the battery...

Quote:

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Originally Posted by pennyman1

Are you running the fans with a relay taking power directly from the battery? That way it does not fry the fusible links. A higher output alternator won't fry the link either - put it back on.

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The fans power came straight from the battery. They have their separate relay. I don't understand it cause it ran fine for a while then blew links back to back?

OK the first one was almost 40 years old. The second one was NOS and that one blew.

How fast did it blow, and what was on at the time?