Good way to omit and replace the fusible link? (1 Viewer)

[chesshircat]

I've replaced most of the cables with 2 & 4 guage cable. I am going to run a new 4 guage wire to the Alt. + and would be a good time to replace the fusible link before it causes a problem. I'd like to completely remove it and maybe somehow tie back into the plate end in the fuse box. Has anyone done something like this

 

[pappy]

I've replaced most of the cables with 2 & 4 guage cable. I am going to run a new 4 guage wire to the Alt. + and would be a good time to replace the fusible link before it causes a problem. I'd like to completely remove it and maybe somehow tie back into the plate end in the fuse box. Has anyone done something like this

I'm going to when I do the 3RZ install since the battery gets relocated. Going with a 100A MIDI fuse since my alt is 80A.

MIDI® Fuses

MIDI® Fuses offer a space saving solution for high current wiring protection. Features a bolt-on design and tin-plated contacts and are available in 30-200 amp options.

www.delcity.net

 

[chesshircat]

I'm going to when I do the 3RZ install since the battery gets relocated. Going with a 100A MIDI fuse since my alt is 80A.

MIDI® Fuses

MIDI® Fuses offer a space saving solution for high current wiring protection. Features a bolt-on design and tin-plated contacts and are available in 30-200 amp options.

www.delcity.net

Do you have a plan to tie into the fuse box?

 

[pappy]

Do you have a plan to tie into the fuse box?

Indirectly. The MIDI fuse will be between the alternator and the battery. Right now the plan is to repurpose the original 10g alternator wire, attached to the battery and running to the original fuse block on the passenger fender just like it does now.

 

[jgranthevagrant]

I moved my start battery to a new location, so I could add a second battery in engine compartment. I kept the original fuse block for the starting battery and added a second block for the house battery, with a fusible link. New fuse block has about 3 MIDI fuses like Pappy mentioned. Basically it mirrors the original fuse block. My truck is a 1990, so the wiring is a bit different from the '85.

 

[chesshircat]

Indirectly. The MIDI fuse will be between the alternator and the battery. Right now the plan is to repurpose the original 10g alternator wire, attached to the battery and running to the original fuse block on the passenger fender just like it does now.

I was thinking about removing the fusible link, use 4awg wire form the battery to a fuse then 4awg from the fuse to the plate in the fuse box where the fusible link was. drill a hole in the plate to bolt the 4awg terminal to the plate? use a fuse the same size as what is in the fuse box?

and 4awg from the Alt. + to 60 amp fuse to 4awg to battery?

 

[chesshircat]

Indirectly. The MIDI fuse will be between the alternator and the battery. Right now the plan is to repurpose the original 10g alternator wire, attached to the battery and running to the original fuse block on the passenger fender just like it does now.

What size fuse are you going to use between the alt and battery?

 

[pappy]

What size fuse are you going to use between the alt and battery?

I upgraded to an 80A alternator, so I'm going to run a 100A fuse.

 

[ntsqd]

One aspect of a fusible link that a fuse can't match is short term over-current tolerance. This is a desirable trait and is why fusible links are used by OEMs instead of a big fuse. To make the fusible links on our CTD not such a PITA to deal with I installed a terminal strip. The supply and load wires attach next to each other and the fusible links jumper across. I made spare links and keep them in the glove box. Makes replacement easy, even in the field.

 

[pappy]

This is a desirable trait and is why fusible links are used by OEMs instead of a big fuse.

Except, on my 4R the fuseable link is a big 80A fuse.

 

[ntsqd]

Then it isn't a fusible link.

There are slow-blow fuses out there. No experience with them. That 80A fuse may or may not be one. Unless marked I know of no way to tell them from 'regular' fuses.

 

[pappy]

Then it isn't a fusible link.

There are slow-blow fuses out there. No experience with them. That 80A fuse may or may not be one. Unless marked I know of no way to tell them from 'regular' fuses.

FSM wiring diagram calls it a "FL 80A."

 

[ntsqd]

Semantics.

 

[toyotaboy80]

I understand why fuses are necessary...but between the alt and the batt, I say just run it unprotected in the fuse department and protected in the abrasion department. The alt will only put out its max(aka size the wire appropriately) and theres nothing pulling off the wire. The only way the wire is a hazard is if it goes to ground. Split loom, ran and secured appropriately, it is a fairly permanent and safe wire to run without a fuse.

Just my opinion.

 

[ntsqd]

The vast majority of vehicles in use concur with you.

It is the power taps at the battery for the rest of the vehicle where fuses and fusible links are typically used.

 

[toyotaboy80]

Yes, and for that, I would fuse it to blow before the wire melts.
I.e if the wire is good for 40 amps, fuse it at 35. The wire will never need to be serviced due to melt, and there should he a handy pack of 35 amp fuses in the glove box to prevent a stranded situation. With a fusible link wire, you're at risk of burning it out completely and being stranded unless you can make that connection on a whim.

As far as I know, a "maxi fuse" is slow blow fuse. Theyre about 4x the size of a traditional automotive fuse. But now you need to run wire big enough to not melt at the slow blow fuses over rated slow blow. At that point, you may as well run what the circuit is rated for. If it fails, you likely went direct to ground. At that point, other corrective action is required so the fuse doesnt blow again. I.e failed component going direct to ground constantly blowing fuses. IMO its unaccaptable to put a slow blow on something. It either failed, or it didnt. I dont want a slow blow 10gauge wire carrying more current than it can handle every other time for a short period of time. That is guaranteed to fail long term.

If the underhood fuse box feeds 80 amps worth of stuff with everything on, feed the box with 90 amp capable wire direct off the battery with a 80 amp fuse. Your supply wire is protected, and the 80 amp fuse is the serviceable component. If things start blowing individual fuses after the fuse box, you have an issue within that standalone circuit.

Bottom line, if youre going to fuse it, the fuse MUST be rated less than the wire, otherwise the wire is the serviceable component.

 

[ntsqd]

The thing to grasp is that the current rating for a given wire at a given length is the continuous duty rating, not the in-rush rating or the short term rating. If the continuous duty rating of a section of wire is 40A it is not going to melt down from a 20 second long, 60A load. A typical fuse will blow with that load, but a fusible link and possibly a slow-blow fuse will not. Maybe that's bad and a fuse should be used, but maybe that is from a very large cooling fan motor and is quite acceptable because once it's running the current is only 37A. Electric motor's starting in-rush currents always exceed their running currents, sometimes by a large margin. I once worked around a 4180VAC 3Ø pump motor that ran on about 100A, but would pin a 250A meter on start-up. Clearly a 100A breaker or fuse would not work for that pump.

 

[jgranthevagrant]

FWIW a pump I just installed required a slow blow fuse. Something to do with being submersed or in a damp environment.

 

[toyotaboy80]

Does increasing the load 50% (40a to 60a) for 20 seconds create enough heat to fail the wire at some point sooner than if a 40a rated wire wasnt ever subject to more than its continuous rating?

Lets say I wired up a 2 speed fan on a wire rated at 40a continuous. Speed 1 pulls 40 amps and speed 2 pulls 60 amps. I would think if I ran speed 2 off a momentary for any amount of time, I would induce premature failure.

 

[ntsqd]

If a 40A load is pulling an in-rush current for 20 seconds something is probably wrong. I used that time above as an extreme example.

Doing a momentary thing like that is very different than allowing in-rush currents in an otherwise too small of a wire. A fan that pulls 60A running will pull much more than that while getting up to speed. The wires would need to be sized for 60A continuous duty over what ever the total circuit length is.

If the wire is getting hot from the current flowing thru it, and it is not a resistance wire designed to do that, then it is undersized and will not likely last very long. The curious thing about wire size and current is that you can move 100A thru an 18 gauge wire without trouble IF you make the wire short enough.