Total electric power loss, intermitent

[rob249]

Ok, so I removed the burned wire, I have a few more questions before I put this all back together. The wire going from the battery to the firewall posts is a pretty large gauge, except for a few inches on the battery end, which is the burned part. The burned wire is a smaller gauge section, but appears to be just regular AWG wire, and not fusible link wire. Is this supposed to be the fusible link section and someone just replaced it with regular wire?

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The top is the battery end, the lower is the firewall end.

On the firewall, I see another wire that says "fusible link" on a different post.

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The post without the wire is where the battery wire went.

So, Do I need to replace the few inch section with actual fusible link wire, or should it just be a regular wire due to the fusible link already on the firewall post? Or are there multiple fuisble links? Thanks.

 

[heskahoka]

Do I need to replace the few inch section with actual fusible link wire

Yes you do. The video I provided recommends the fusible link 4 gauges smaller than the feed wire. (Example, if the Feed wire is 10 gauge, the fusible link wire should be 16 gauge.)

Or are there multiple fuisble links?

Yes, there can be multiple fusible links in a harness.

 

[Schurkey]

Yes you do. The video I provided recommends the fusible link 4 gauges smaller than the feed wire. (Example, if the Feed wire is 10 gauge, the fusible link wire should be 14 gauge.)

FIFY. 10 + 4 = 14. 14-gauge fusible link protects a 10-gauge wire.

Yes, there can be multiple fusible links in a harness.

But not on a single wire.




If someone has already repaired this wire once (improperly, using non-fusible-link wire) and it's popped again...what else is overloading that wire to cause so much current flow? Is that wire supplying power to a failing circuit? Aftermarket accessories?

 

[rob249]

No aftermarket accesories yet, all stock. When I bought the truck, It was wired for a sound system, with a huge 4 gauge-ish fused wire going to the back where he had a sub. I removed the fuse and disconnected the wire years ago. The fusible link wire is heavily corroded, as is the alternator wire. The Alt wire is only 12 gauge, which seems very small for a 105 amp alternator. I just replaced the alternator wire with a 10 gauge, which still seems small.

edit; Just out of curiosity, whats the reason for using a fusible link instead of a regular fuse or even a breaker?

 

[heskahoka]

FIFY. 10 + 4 = 14. 14-gauge fusible link protects a 10-gauge wire.

You are correct. Thanks for the fix.

 

[heskahoka]

Just out of curiosity, whats the reason for using a fusible link instead of a regular fuse or even a breaker?

They were flexible, heat tolerant and most of all - cheap. A product of their times. Used a lot in older vehicles, but not now. Who wants to go on a burnt wire treasure hunt in a modern car !

 

[Schurkey]

A fuse--even a slow-blow fuse--pops almost instantly in an overload situation.

Circuit breakers are "expensive".

A fusible link will handle a short-term overload without failing, yet still opens to protect the circuit if the overload lasts a longer time. Eliminates "nuisance" circuit disconnects and fuse replacement/breaker resetting when the overload is of short duration.

 

[Erik the Awful]

The selling point on fusible links is that the insulation is supposed to remain intact when the metal inside melts. About half the fusible links I've seen blow melted right through the insulation. They're garbage, but they're also cheap and while good they're dead-nuts reliable.

I replaced the fusible links in my son's truck with a row of maxi-fuses, and the connector kept coming loose. I finally relented and spliced in fusible links because they're not near anything flammable. It runs

The recommendation I've seen is to run no more than 6" of fusible link in a single wire.

 

[Schurkey]

The selling point on fusible links is that the insulation is supposed to remain intact when the metal inside melts. About half the fusible links I've seen blow melted right through the insulation. They're garbage, but they're also cheap and while good they're dead-nuts reliable.

That's the idea--the wire conductor melts, the insulation stays intact.

If that's not happening, I'd think there'd be some product-liability lawsuits.

Been so long since I've seen a popped fusible link, I don't have any recent experience with them.

The recommendation I've seen is to run no more than 6" of fusible link in a single wire.

I'm digging around in the '97 C/K service manual. Specifically, starting on 8A-5-0, but getting really relevant at 8A-5-2. The manual lists all sorts of circuit protection devices including one I didn't know the name of--Pacific Fuse Element.

Anyway, there's three kinds of fusible link insulation types listed in the manual:
Hypalon (Same color insulation all the way through.)
Silicone/GXL (Colored outside, white inside. Kinda like a Twinkie.)
Expanded Duty (Same color insulation all the way through, but has three dots printed along with whatever writing is inked-onto the insulation.)

Hypalon links can only replace Hypalon links. Silicone GXL can replace Silicone GXL or Hypalon. Expanded Duty can replace all three types. I have no idea what the functional difference is among these three types of insulation.

GM suggests that if fusible link wire is to be cut from a spool, to use 6--9 inches, but never more than 9 inches. If buying a pre-made fusible link wire, use the shortest length "suitable".

I've been making my fusible links 4--6 inches long, and generally closer to 4 than to 6. Guess I'll have to add some length in the future.

 

[rob249]

I replaced mine with about 4" of fusible link wire(14g), about the same as what was there. Unfortunately, after erroneously replacing my ignition switch, it now wont engage the starter. I know its adjustable, but sliding it all the way back still doesnt engage the starter. My lock cylinder needs replacement anyway, so im going to do that now. Maybe my crappy lock cylinder isnt pulling that rod far enough?