Fusible Links vs Maxi Fuse

[dsteelejr]

I'm looking for some opinions from people with wiring experience.

I'm redoing most of the wiring on my square. It's an '80 K25 454. I decided to forego buying a pre-made wiring harness and do it wire by wire. I plan to keep the wiring pretty close to stock, with a few minor deviations. On the primary power circuits I am going to run power from the starter to a power distribution block on the firewall. I'm on the fence about whether to run two 10 AWG wires with fusible links or run a single 6 AWG wire with a a 60 or 70 amp inline maxi fuse as close to the starter as possible to the power distribution block.

I know the how's and why's of fusible links, but I haven't come across very much literature on the subject except that most, if not all, late model vehicles use maxi fuses instead of fusible links and quite a few owners across the entire car community have upgraded their rides from fusible links to maxi fuses.

Any thoughts?

 

[C10MixMaster]

I'm looking for some opinions from people with wiring experience.

I'm redoing most of the wiring on my square. It's an '80 K25 454. I decided to forego buying a pre-made wiring harness and do it wire by wire. I plan to keep the wiring pretty close to stock, with a few minor deviations. On the primary power circuits I am going to run power from the starter to a power distribution block on the firewall. I'm on the fence about whether to run two 10 AWG wires with fusible links or run a single 6 AWG wire with a a 60 or 70 amp inline maxi fuse as close to the starter as possible to the power distribution block.

I know the how's and why's of fusible links, but I haven't come across very much literature on the subject except that most, if not all, late model vehicles use maxi fuses instead of fusible links and quite a few owners across the entire car community have upgraded their rides from fusible links to maxi fuses.

Any thoughts?

I rewired mine using fusible links but in retrospect I wish I would have done maxi fuses. I've never been a fan of fusible links..

 

[AKguy]

I would use the Maxi Fuse, or similiar. Although I have never experienced a fusible link failure, why not make it easy to fix?

 

[Camar068]

Just a thought, but I'd get a top and side terminal battery, and run another cable to a hefty positive/negative blocks on the firewall and go from there. Use top for starter and side for everything else or visa versa. One less cable around the exhaust and on the starter to deal with.

 

[Matt69olds]

Maxi fuses are so much easier to repair. However, fusible links or maxi fuses shouldn’t blow unless something is seriously wrong.

Replace the links with fuses, put the fuse holders someplace fairly easy to access. Then you can pull fuses instead of disconnecting battery cables during routine service. You can also remove fuses for anti-theft.

 

[Memaloose]

Amen on the fuses. If a link goes, it usually takes other wires with it and makes a melted mess! Plus, thet're hard to find. I've never had a problem on GM products, most Ford.

 

[Scott91370]

I hadn't thought about this but I like the idea.
The only question I have, so far, is how do you determine what size fuse is needed? @dsteelejr mentioned using a 60 or 70 amp but how did you come up with that?

 

[dsteelejr]

I hadn't thought about this but I like the idea.
The only question I have, so far, is how do you determine what size fuse is needed? @dsteelejr mentioned using a 60 or 70 amp but how did you come up with that?

Stock 63 amp alternator. Fusing 10% over 63 amps is 69 amps.

I figure if you can remove the battery from the vehicle after its started and the alternator can supply enough juice to keep the vehicle running it would be safe to fuse it for the alternator’s rating.

 

[Corvette Ed]

As others have said,go with fuses.

 

[C10MixMaster]

Stock 63 amp alternator. Fusing 10% over 63 amps is 69 amps.

I figure if you can remove the battery from the vehicle after its started and the alternator can supply enough juice to keep the vehicle running it would be safe to fuse it for the alternator’s rating.

I would base fuses on the wiring they are protecting not what they are powering.

 

[dsteelejr]

I would base fuses on the wiring they are protecting not what they are powering.

This is to replace fusible links for the primary power coming off the starter. This is to protect the whole electrical system and keep the truck from burning down if there is a major short to ground somewhere under the hood.

 

[DoubleDingo]

Maxi!

 

[Matt69olds]

If I remember correctly, there are 2 main power feeds on the starter solenoid. One feeds the ignition, headlights, charging system, etc, the other is for electrical power to turn signals, heater, etc.

Put a power distribution block near the battery with one large cable from the positive post to the distribution stud. Branch off of the stud with smaller cables to the maxi fuse, each fuse powering a circuit originally protected by a fusible link. I would think 50 amps would be plenty.

On my Olds, I have a Ford starter solenoid mounted on the firewall near the fuse panel. All the high current things (nitrous bottle heater, power windows, charging system, etc) are connected to the battery side of the solenoid, protected with appropriate fuses. The only remaining fusible link is on the alternator output. I have a 105 amp alternator, with a 6 gauge wire to the solenoid. It’s protected by a 10 gauge fusible link.

I built the dash harness from scratch using a fuse box from a square body truck. The power feeds to the fuse box are on a 60 amp maxi fuse. I can pull that maxi fuse and kill all power to the fuse panel. I also got creative, I put the power feed to the clock and radio presets on a separate circuit protected by a 5 amp fuse that is on the battery cable side of the solenoid.

Whenever I have the door open for a long period of time, I pull the maxifuse. That kills all power to the interior. Since the clock and radio presets are on a separate circuit independent of the maxi fuse, the clock and presets stay powered. I got tired or resetting things whenever I had to disconnect power.

 

[dsteelejr]

If I remember correctly, there are 2 main power feeds on the starter solenoid. One feeds the ignition, headlights, charging system, etc, the other is for electrical power to turn signals, heater, etc.

Put a power distribution block near the battery with one large cable from the positive post to the distribution stud. Branch off of the stud with smaller cables to the maxi fuse, each fuse powering a circuit originally protected by a fusible link. I would think 50 amps would be plenty.

On my Olds, I have a Ford starter solenoid mounted on the firewall near the fuse panel. All the high current things (nitrous bottle heater, power windows, charging system, etc) are connected to the battery side of the solenoid, protected with appropriate fuses. The only remaining fusible link is on the alternator output. I have a 105 amp alternator, with a 6 gauge wire to the solenoid. It’s protected by a 10 gauge fusible link.

I built the dash harness from scratch using a fuse box from a square body truck. The power feeds to the fuse box are on a 60 amp maxi fuse. I can pull that maxi fuse and kill all power to the fuse panel. I also got creative, I put the power feed to the clock and radio presets on a separate circuit protected by a 5 amp fuse that is on the battery cable side of the solenoid.

Whenever I have the door open for a long period of time, I pull the maxifuse. That kills all power to the interior. Since the clock and radio presets are on a separate circuit independent of the maxi fuse, the clock and presets stay powered. I got tired or resetting things whenever I had to disconnect power.

Sounds like you have it all figured out.

My square is just a base model, no A/C, no power windows, no power locks, etc. so I don’t have any high current circuits other than the starter itself and the charging system.

I was planning on using another inline maxi coming off the alternator and run it along the valve cover with the exciter wires and electric choke wire. I’m planning on using a four post junction block bus so I don’t have so many wires on one stud. Locating the
junction block on the fire wall seems to work best for my situation because everything is mostly stock so all the power wires need to make their way into the cab, but I’m intrigued with the set up you described. It caffeinated the hamster in my head and got me thinking. I’ve been planning this for several weeks now and I’ve changed my plans several times and I may change them again.

Thanks to everyone for the input!

 

[Nuckollsr]

Fusible links are not fuses . . . they are current limiters intended to protect relatively fat wires that carry power to distant distribution points, usually fuse blocks where the power splits out to various appliances and sundry tasks around the vehicle. Fusible links are simply pieces of ordinary copper wire sheathed in an insulation that stands up to molten copper within while producing a minimum of low toxicity smoke. These insulations were developed for the electric locomotive industry where humans shared close proximity with at-risk wires carrying a LOT of current. The fusible link is sized at four wire-gauges smaller than the protected feeder. I.e. a 10AWG feeder should get a 14AWG fusible link at the BATTERY end of the feeder. In some cases where the feeder supplies a single load, no additional fusing is necessary for protection of the wires. But it may well be that a fuse-block at the downstream end of the feeder will carry fuses appropriate to the load of each circuit.

Fusible links are VERY slow acting compared with fueses as you might guess from their construction. They are NOT interchangeable. Most of the explanations on the 'net are simplistic and miss the point for incorporation of SLOW fuses in a power distribution system. Worked in aircraft for the last 50 years and while we don't use fusible link wire, we DO use very slow, robust current limiters that kinda look like a fuse . . . but they're not.

You will note that fusible links are 'rated' by AWG wire size, not AMPs like a fuse.