FJ60 Burnt Fusible Link Fuse replacement / Rewire (1 Viewer)

[FJ60binh]

Hi everyone I just want to share how I have modernized my Fusible Link, my fuse amp choices, and wire size choices.

I have a hand drawn 3 diagrams:

1) is a DIY by fellow forum member chriscwill07 of his version. (Thank you Chris, very helpful).
2) is the OEM fusible link garbage
3) is my own solution using a 10 amp a 40 amp and a 15 amp fuse.

Long story: I bought my FJ60 with a faulty charging system it was just an old battery. 2 batteries later i realized that the wire in the fusible link that charges my battery from the alternator is burnt out. First I tried Chris's style with 3 40amp fuses, but when i accidentally shorted the system, it burnt out a wire instead of my fuses. I began to switch to smaller fuses. Using the OEM fusible link wire thickness, I calculated it's thickness in gauge and matched the wire sizes 10 amp, 40 amp, 15 amp. I have not had any problems charging! Cheers!

Fj6

 

[FJ60binh]

Sorry for the typos and grammar. I have not unlocked Editing

I have one final diagram drawing to make it more clear.

 

[NookShneer]

If the plastic connector housings are in good shape. I would rebuild the existing link with the correct fusible link wire and terminals.

 

[duncanrm]

Nice work well done! I did something similar, definitely superior to the original fusible links.

 

[CruiserTrash]

If I’m reading this correctly, there’s a 15 amp fuse for all lighting and everything else serviced by the cabin fuse box?

The headlights are 60 watts each with the high beams on, 120 watts together. Divide by 12.6V for the current draw at idle, 9.52A. That leaves 5.48A for everything else. Seems a bit undersized. Then again the wiring was undersized to begin with and it’s probably worthwhile to protect that from starting a fire.

For the alternator how did you choose 40A? The stock alternator is capable of supplying 55A at high rpm & low battery charge, and those conditions might cause it to blow.

Not trying to nitpick, just thinking out loud here.

 

[BurntToast]

Glad to see another modern replacement of old tech. I talked with a few electrical engineers recently on the topic, all agreed no reason not to find the right rating and replace with a modern fuse setup.

 

[FJ60binh]

If I’m reading this correctly, there’s a 15 amp fuse for all lighting and everything else serviced by the cabin fuse box?

The headlights are 60 watts each with the high beams on, 120 watts together. Divide by 12.6V for the current draw at idle, 9.52A. That leaves 5.48A for everything else. Seems a bit undersized. Then again the wiring was undersized to begin with and it’s probably worthwhile to protect that from starting a fire.

For the alternator how did you choose 40A? The stock alternator is capable of supplying 55A at high rpm & low battery charge, and those conditions might cause it to blow.

Not trying to nitpick, just thinking out loud here.

I based it on the existing wire size in the Harness. If i had ran a higher Amp fuse, it would burn my wire instead of my fuse. Thanks for the input ! i appreciate it.

 

[georgebj60]

How is this protected from the elements? Is your fuse case and connections inside another box? Sorry if this is a stupid question, but I do need to look at updating my fusible links in my HJ60 so I'm keen to get as much info as possible.

 

[BurntToast]

I based it on the existing wire size in the Harness. If i had ran a higher Amp fuse, it would burn my wire instead of my fuse. Thanks for the input ! i appreciate it.

Exactly, fuses are sized to protect the wire, not the load. The wire harness is sized to power the loads

 

[CruiserTrash]

I based it on the existing wire size in the Harness. If i had ran a higher Amp fuse, it would burn my wire instead of my fuse. Thanks for the input ! i appreciate it.

There’s also the downstream fuses for individual components to protect the wire too it’s a balance, and takes intentional thought towards the purpose of each fuse. Say we have a runaway current situation in the headlight system - a 12V wire’s insulation has been compromised and the wire is touching the body (ground) - the 15A fuse in the cabin should blow and protect that wiring. So what’s the fusible link for? To protect the wiring run between the battery and fuse box? To protect against jumper cables put on the battery wrong? I’ve done that one!

In full disclosure I’m close to releasing a fusible link replacement product for non-electrically-minded people. You know, 20 minute install using no special tools, something you could teach a monkey to do. It’s easy enough for someone with electrical experience to homebrew, but a lot of folks are scared of doing stuff like this. A “kit” would be helpful to them.

 

[BurntToast]

There’s also the downstream fuses for individual components to protect the wire too it’s a balance, and takes intentional thought towards the purpose of each fuse. Say we have a runaway current situation in the headlight system - a 12V wire’s insulation has been compromised and the wire is touching the body (ground) - the 15A fuse in the cabin should blow and protect that wiring. So what’s the fusible link for? To protect the wiring run between the battery and fuse box? To protect against jumper cables put on the battery wrong? I’ve done that one!

In full disclosure I’m close to releasing a fusible link replacement product for non-electrically-minded people. You know, 20 minute install using no special tools, something you could teach a monkey to do. It’s easy enough for someone with electrical experience to homebrew, but a lot of folks are scared of doing stuff like this. A “kit” would be helpful to them.

Looking forward to it. Basing is off a Bluesea box?

 

[CruiserTrash]

Looking forward to it. Basing is off a Bluesea box?

Blue Sea stuff is great, but there’s a different box that’s perfect for this application. It’s high quality and IP- rated waterproof. There will be a custom designed bracket for it as well. Awaiting prototypes of two variations of that to arrive in the mail right now.

Back to your system … I think it’s probably safer than it needs to be, which is completely fine. I have a feeling some of the fuses might blow prematurely and often as you first start using it, but you can walk the fuse sizes up in increments to find a safe value that doesn’t present false positive failures. We won’t know until you put it in service though. The true test will be headlights, blinker, HVAC blower, rear defrost, etc, all running while the truck is at idle. And the same test at highway speeds to check the alternator fuse. The install is clean too, looks great. Somebody above mentioned waterproofing, but if you’re not fording water - maybe your truck is just a daily driver - I bet you’ll be fine. Plenty of protection from rain above or below, being kicked up by the tires.

Last thing, are those ATC fuses? Do you know the blow speed on them? Fusible Links are pretty slow so that they don’t continually pop from high inrush current events (like flipping on the headlights), yet they will still blow within 30-60 seconds for certain current levels. Best to find something with a similar speed curve.

 

[FJ60binh]

Blue Sea stuff is great, but there’s a different box that’s perfect for this application. It’s high quality and IP- rated waterproof. There will be a custom designed bracket for it as well. Awaiting prototypes of two variations of that to arrive in the mail right now.

Back to your system … I think it’s probably safer than it needs to be, which is completely fine. I have a feeling some of the fuses might blow prematurely and often as you first start using it, but you can walk the fuse sizes up in increments to find a safe value that doesn’t present false positive failures. We won’t know until you put it in service though. The true test will be headlights, blinker, HVAC blower, rear defrost, etc, all running while the truck is at idle. And the same test at highway speeds to check the alternator fuse. The install is clean too, looks great. Somebody above mentioned waterproofing, but if you’re not fording water - maybe your truck is just a daily driver - I bet you’ll be fine. Plenty of protection from rain above or below, being kicked up by the tires.

Last thing, are those ATC fuses? Do you know the blow speed on them? Fusible Links are pretty slow so that they don’t continually pop from high inrush current events (like flipping on the headlights), yet they will still blow within 30-60 seconds for certain current levels. Best to find something with a similar speed curve.

This is a good point. Now that you have brought this up, making a Jcase fuse panel for this would be better than using ATC fuses. I'll have to add that to my to do list. Thanks mate!

 

[FJ60binh]

How is this protected from the elements? Is your fuse case and connections inside another box? Sorry if this is a stupid question, but I do need to look at updating my fusible links in my HJ60 so I'm keen to get as much info as possible.

It's not I need to make a casing or something to protect it from the element

 

[CruiserTrash]

It's not I need to make a casing or something to protect it from the element

I'll put it this way: the battery terminals aren't encased in a waterproof enclosure, and this mounts right next to it. It's protected by the hood, by the wheel well rubber flaps, and by a dust-resistant plastic top. Like I said, if you aren't doing deep river crossings I bet your setup will be plenty good.

 

[TreadingLight]

Last thing, are those ATC fuses? Do you know the blow speed on them? Fusible Links are pretty slow so that they don’t continually pop from high inrush current events (like flipping on the headlights), yet they will still blow within 30-60 seconds for certain current levels. Best to find something with a similar speed curve.

Like fusible link wire! I get the drive to modernize bit I would really want to avoid fast blowing fuses. Prematurely blowing a fuse on the highway could lead to a real bad day.

I rebuild mine using fusible link wire. Size it by choosing a wire gauge 4 sizes smaller than the wore it protects (ex: 12g fusible link to protect an 8g wire). The fusible link wire has a jacket that is flame retardant so it can melt safely in the event of a short.

 

[CruiserTrash]

Like fusible link wire! I get the drive to modernize bit I would really want to avoid fast blowing fuses. Prematurely blowing a fuse on the highway could lead to a real bad day.

I rebuild mine using fusible link wire. Size it by choosing a wire gauge 4 sizes smaller than the wore it protects (ex: 12g fusible link to protect an 8g wire). The fusible link wire has a jacket that is flame retardant so it can melt safely in the event of a short.

There’s definitely an argument for rebuilding the originals… I’ve done a few and it’s not too hard. It does take a little longer than swapping a fuse though, so pick your poison.

 

[CruiserTrash]

Ok, here it is: The Fusible Link Replacement Kit


I figured out the current capacity of the OEM wires in the harness, figured out the protection capabilities of the fusible link wire sizes, then checked out derating curves and time-current curves to come up with the properly sized MIDI fuses. These blow pretty slow like the link wire but just a touch faster, so they provide greater safety without blowing during inrush current or slight overages.

The kit is 100% plug & play. Bolt a bracket to your inner fender, screw the fuse panel down to the bracket, attach a ring terminal on the battery on one end, and plug a round connector into the harness connector on the other end.

What you get:
-Custom stainless steel bracket
-Overland Metric plated JIS hardware
***the following is pre-assembled:
-Littelfuse IPXK9 waterproof fuse panel (rated for direct spray with high pressure water)
-Littelfuse MIDI fuses (these are tested and have datasheet unlike cheapo Amazon fuses)
-6awg marine grade main batter cable
-Brand new Yazaki wire (same kind of wire Toyota originally used on 60 Series trucks)
-Waterproof/sealed Sumitomo connector
-Overland Metric plated JIS hardware
-Optional 6awg alternator charge cable (helps bring up system-wide voltage at idle by around 0.5V)

 

[TreadingLight]

Is it plug n play for a 62? I can't remember if the plugs are the same.

 

[CruiserTrash]

Is it plug n play for a 62? I can't remember if the plugs are the same.

No, this doesn’t fit a 62 application but I’m working on that. The bracket will not fit a 62 because the air cleaner is in the way, and the 62 has 5 fusible links rather than the 3 in the 60. Coming soon, maybe a couple months from now.