Convert from fusible link to fuse or circuit breaker - discussion

[Seth S]

Figured I'd create a thread on this topic as it cropped up in another thread. I'm pretty sure I've seen a few build threads where people have replaced the fusible link setup with either a fuse block or circuit breakers. I think this is a great idea for people who may be upgrading their wiring and want to go a different route than the stock.

I found this table which I might be able to use to reverse engineer one of my fusible links:

 

[OSS]

If a fusible link burns out at 60 Amps or a slow blow fuse blows out at 60 Amps, they’re both doing the same thing. Probably 99.8% of vehicles never short out their wiring harness to blow a FL so it likely was a cost cutting design choice to fuse (link) the wiring harness right next to the battery terminal. Either method will work (fuse or link), the link was probably just a more streamlined solution.

 

[Seth S]

If a fusible link burns out at 60 Amps or a slow blow fuse blows out at 60 Amps, they’re both doing the same thing. Probably 99.8% of vehicles never short out their wiring harness to blow a FL so it likely was a cost cutting design choice to fuse (link) the wiring harness right next to the battery terminal. Either method will work (fuse or link), the link was probably just a more streamlined solution.

100% it makes sense for an automotive supplier to use a fusible link as its simple and basically free in the grand scheme of things. I'm just thinking of making the engine bay more modern and a little cleaner a set of circuit breakers would be a nice upgrade....I know I've seen some Mudders reports on doing it...just cant find them at the moment.

 

[OSS]

A turn-key wiring harness fuse/breaker replacement kit for that yucky fusible link would be welcomed by probably everyone

 

[george_tlc]

MIDI fuses will give a similar 'slow' blow response as a fusible link. A MIDI fuse can handle a reasonable overload condition for a short period of time similar to how a fusible link would function. I retrofitted my old patrol in oz with MIDI for various reasons (upgrades, change from 24V to 12V operation, etc).

Given that the fusible link is your last line of defence in case of a catastrophic short somewhere in the wiring, I'd rather trust a MIDI/fusible link for that situation.

cheers,
george.

 

[JamesR]

A buddy of mine shared this with me.
Its a circuit breaker fuse.

Amazon product

 

[OSS]

Maybe a Landcruiser, being what it it’s - designed for extreme off road use with extreme vibration, falls into a different category than regular vehicles when it comes to protecting the wiring harness. Maybe a fusible link IS the best design choice for extreme off-road use. They’re pretty much bulletproof

 

[george_tlc]

A buddy of mine shared this with me.
Its a circuit breaker fuse.

Amazon product

Be careful. You need to read through the specs to understand the device before just swapping something in.

Looking at the Bussmann spec, at 65C (likely a hot day in a hot engine bay), they derate the current spec by 50%. The 20A could trip at 10A... A MIDI fuse at 65C (refer to the Littelfuse spec) derates less than 5%, i.e. a 20A MIDI at 65C is spec'd to handle 20A x 0.95 = 19A.

Also, a MIDI is well defined in terms of when it fuses based on overcurrent. If you check the Bussmann spec for that breaker, it is quite a wide value. God knows the Amazon 'clone' spec...

The whole point of the fusible link is to provide protection for the wiring harness. The individual circuit fuses protect the devices/feeds from the main fuse source wiring.
It is a hierarchical system that is engineered. Don't second guess it - last thing you want is a serious harness failure, especially out in the sticks. Or a breaker that trips prematurely.

cheers,
george.

 

[Bike n Board Cruiser]

The old parts can usually be cleaned up pretty good. The spades are a weird size. They are like 7.2 instead of the common 6.5 you will find online. I have the ability to create what you see in this photo. Sending your parts to me would be required but it keeps a Toyota like fusible link on your truck. Melted parts would obviously not be reusable so time to source an equivalent would take time if yours are melted.

 

[Seth S]

So the current FL runs a leg of protection to the alternator and to the main wiring harness. The starter remains a continuous heavy cable. In an alternate setup I'd wonder if just putting a protection device between the battery and the alternator would be enough to protect everything. The Alternator is the only thing capable of producing too much voltage/amperage by way of a V reg failure. If the Alt Overamps and triggers a fuse or circuit breaker then the truck would still run off the battery for a time. The Bat light would need to come on to indicate a problem but the rest of the circuits would be fine. yes no?

 

[OSS]

A short downstream of the FL but before the fuse block will melt the wiring harness if there’s no FL to protect it. Possibly catch the vehicle on fire. The primary culprit would be wires chafing against the body somewhere under the dash before the fuse block. Easy enough to do if living on washboard roads.

 

[Seth S]

A short downstream of the FL but before the fuse block will melt the wiring harness if there’s no FL to protect it. Possibly catch the vehicle on fire. The primary culprit would be wires chafing against the body somewhere under the dash before the fuse block. Easy enough to do if living on washboard roads.

Makes sense.

 

[moclakens]

This seems worth bumping as I cannot find any new fusible links in stock.. well I found a few examples in stock on eBay for $250..

The way I am reading this chart I would need two 15 or 20 amp fuses for the body harness to closely mimic the original configuration?

Seems like something like the SafetyHub 150 would be a nice box to run everything though with some room to expand later. Would also make a nice way to do a direct run from the body to alternator.

Blue Sea 7748 Safetyhub 150 Fuse Box

BLUE SEA 7748 SAFETYHUB 150 FUSE BLOCKSafetyHub 150 Fuse BlockThe SafetyHub 150 is an ignition protected fuse block with screw termination. It is safe for use on gasoline powered boats, reduces wiring connections, and consolidates upt to ten fused ci...

www.hodgesmarine.com

 

[BurntToast]

This seems worth bumping as I cannot find any new fusible links in stock.. well I found a few examples in stock on eBay for $250..

The way I am reading this chart I would need two 15 or 20 amp fuses for the body harness to closely mimic the original configuration?

Seems like something like the SafetyHub 150 would be a nice box to run everything though with some room to expand later. Would also make a nice way to do a direct run from the body to alternator.

Blue Sea 7748 Safetyhub 150 Fuse Box

BLUE SEA 7748 SAFETYHUB 150 FUSE BLOCKSafetyHub 150 Fuse BlockThe SafetyHub 150 is an ignition protected fuse block with screw termination. It is safe for use on gasoline powered boats, reduces wiring connections, and consolidates upt to ten fused ci...

www.hodgesmarine.com

I’ve been tempted by this one. Someone needs to sacrifice their fusible links with a power supply to get some real data on when they blow.

But there are other threads that talk about what size maxi/midi fuses would be appropriate. I’ll have to see if I bookmarked them

 

[Spook50]

This seems worth bumping as I cannot find any new fusible links in stock.. well I found a few examples in stock on eBay for $250..

The way I am reading this chart I would need two 15 or 20 amp fuses for the body harness to closely mimic the original configuration?

Seems like something like the SafetyHub 150 would be a nice box to run everything though with some room to expand later. Would also make a nice way to do a direct run from the body to alternator.

Blue Sea 7748 Safetyhub 150 Fuse Box

BLUE SEA 7748 SAFETYHUB 150 FUSE BLOCKSafetyHub 150 Fuse BlockThe SafetyHub 150 is an ignition protected fuse block with screw termination. It is safe for use on gasoline powered boats, reduces wiring connections, and consolidates upt to ten fused ci...

www.hodgesmarine.com

If you're wanting to convert, this does look like a good option.

If you're wanting to stick with the OEM fusible links, you can get very high quality reproductions from both @ToyotaMatt and @torfab

 

[BurntToast]

This seems worth bumping as I cannot find any new fusible links in stock.. well I found a few examples in stock on eBay for $250..

The way I am reading this chart I would need two 15 or 20 amp fuses for the body harness to closely mimic the original configuration?

Seems like something like the SafetyHub 150 would be a nice box to run everything though with some room to expand later. Would also make a nice way to do a direct run from the body to alternator.

Blue Sea 7748 Safetyhub 150 Fuse Box

BLUE SEA 7748 SAFETYHUB 150 FUSE BLOCKSafetyHub 150 Fuse BlockThe SafetyHub 150 is an ignition protected fuse block with screw termination. It is safe for use on gasoline powered boats, reduces wiring connections, and consolidates upt to ten fused ci...

www.hodgesmarine.com

so like Georgle_tlc said above, derating for temp is important. Here is the midifuse chart and Datasheet

Here is the fusible link diagram from the FJ62

Per Coolerman
".5mm fusible link = 20ga fusible link
.85 mm fusible link = 18ga fusible link
1.0mm fusible link = 16ga fusible link
1.25mm fusible link = 16ga fusible link
2.0mm fusible link = 14 ga fusible link"

So assuming the "4 number" difference:
0.85R Yellow is protecting a ~14ga wire
0.5G Red is protecting a ~16ga wire
1.25B White is protecting a ~ 12ga wire
0.5G Black is protecting a ~16ga wire
0.5G Black/Green is protecting a ~16ga wire

If nominal and max currents on each one of those could be measured, a suitable fuse could be selected. Their are standard ratings for each gauge of wire, but it dependent on length

 

[CruiserTrash]

I got R&D/plans in the works for a bracket that holds a fuse box that replaces the FL. This would be a 10-minute-install kind of deal using factory threaded holes, with fuses rated exactly to the original fuse wire spec. CAD work is partially done and I need to select the best fuse box and figure out one wiring piece. Stay tuned.

 

[Spook50]

I got R&D/plans in the works for a bracket that holds a fuse box that replaces the FL. This would be a 10-minute-install kind of deal using factory threaded holes, with fuses rated exactly to the original fuse wire spec. CAD work is partially done and I need to select the best fuse box and figure out one wiring piece. Stay tuned.

Curious to see how this comes out. You developing for the 60 or 62 series?

 

[FJ Silver]

I swapped my inline fuses for a regular Blue sea fuse box a few years back without any issues if someone is on the fence.

 

[CruiserTrash]

Curious to see how this comes out. You developing for the 60 or 62 series?

Likely the 60 first as 62 links are still available.