Hello All,

Upon coming through the wiring and rewiring a good amount of the truck I have slowy but surely been removing old cabling and their fuseable link counterparts. Has anyone found a chart or list of roughly what amperage the old links were handling so I can put the approriate size fuses in the circuits?

Thank you.

 

this might help...a fusible link is normally 3-4 gauges smaller than the wire/circuit it protects.

https://www.powerstream.com/wire-fusing-currents.htm

 

I'd maybe just carry new replacement fusible links with me in a box. They don't wear out, they just blow if needed.

 

Right but without knowing the gauge of the wire short of measuring and counting strands I would assume we taking educated guesses here? I think the problem is me not knowing exactly what Ford installed to determine that and would require great many maths to physically verify that unless someone has put in the work to verify each link and estimate the load calc on the circuits assuming factory setup. It would nice if there was a conversion chart or something saying " oh lighting circuit A has x amount of links in the branch each is x amount and your new EOL fuse should be x."

Maybe I need to just energize the circuit, pull out the amp clamp, do the math per circuit and select from there. I think most of the circuits with the links run back to the engine bay some way or another. so maybe I'll put a multi midi block fuse holder somewhere in there.

I think on the hot mess that was a branch circuit involing the lighting, horn, alt., regulator and ignition circuit all of that tied into a fuseable link and working through the circuit more links are through out the chain. I think one of the bigger BLK/YLW cables I had 2-3 links just on that while also branching out at each link to other circuits with variying gauges of wire throughout the runs.

I am not replacing the fuseble links, I would rather have a predictable known fuse accesable either at the battery or near my fuse panel instead of finding them buried in a taped up wiring harness every two feet in fun places to access and cutting the rubber when I need to verify they haven't given up the ghost.

Sorry if winded, I stay up way too late wondering about electrical shennanigans, its my day job.

 

I think a look in the Master Parts Catalog could show a part number for each fuseable link and in the margins may be further information. I think they list parts of the wiring harness in the MPC text and illustrations. I would think if you approached it like designing a circuit you wish to add you can easily predict the parameters built into a circuit that contains a fusible link..

 

I would keep the fusible links. Replace any that are not in good condition. I've been driving since 1975. I've replaced exactly ONE fusible link (on a Dodge car, in 1977 or 1978). Trying to install inline fuse holders is a can of worms, and there's no way to keep moisture and corrosion out of them, no matter how "weatherproof" they claim to be. I use high-quality "weatherproof" blade-type fuse holders in the engine compartment of my vehicles in the heavy power leads to my amateur radio equipment. I keep having to pull the fuses and clean the contacts and periodically replace the fuse holders due to corrosion. I've never found a good way around this issue.

 

These "GEP" products work really well the connectors are all sealed going into the box and the box has a really good seal on it also. They make them in many configurations and circuit capacities and they're stackable.

 

Fusible links have their own characteristics, and as pointed out, probably have a couple of benefits under the hood.
But I’m not completely against replacing them with Fuses, as I’ve stated recently in another thread. But a question would be, if you’re rewiring things, how come you don’t know what gauge it is?
If it’s original, there is a gauge marked in some places. Not every wiring diagram lists it, but I saw one posted up recently that looked like a factory diagram that also had gauge size clearly next to the circuit.
If you can find diagrams like that, you’re set.
Obviously if you’re replacing the wire, you must know what size it is.

Typically, with the Ford main cabin power wire, and typically the charge wire, it’s black, or black with yellow, and is 10 gauge. Protected by a 14 gauge fusible link.
Aftermarket harnesses also use 10 gauge in this position, and typically claim that, depending upon the length of course, it’s good for up to 100 A for a short time.
That coincides with some trucks and cars having 100 amp alternator option in some cases.
And I don’t think Ford changed the size of the wire to compensate for the larger optional setup.
But remember the biggest standard alternator at the time was 55 A, and the biggest fuse I’ve ever seen used in an aftermarket harness to protect the main circuit was 60 A.
You can factor in your needed use, by what you have to work with. If you total up everything running at the same time, such as headlights on high, heater motor on high, brake lights, windshield wipers, and a couple of dome lights, and other things, you can probably figure out how much load would be a maximum on your power feed line.
Assuming the 10 gauge wire could handle 80 A for example, but your maximum load is only 45, a 60 amp fuse would seem to be perfect.
I would bet in some of the older trucks, a 40 or 50 amp fuse is more than enough.
You definitely want to protect the wire, and fusible link is probably a “slow blow” kind of protection, given that it relies on overheating of a wire.
Whereas a fuse is, usually anyway, a quick blow type of protector.
Then again, you could always use a 60 amp circuit breaker and be done! :-) 🙄

Another circuit typically protected by a fusible link is the horn power feed to the relay.
It’s usually connected to the starter relay and I believe it is a 12 or 14 gauge wire.
You could probably protect it with a 25 or 30 amp fuse, but the slow blow aspect of a usable link probably has an advantage here. If you haven’t already cut it out, and it’s not compromised, you might just keep it for simplicity and cleanliness.
Horns take a lot of energy to honk, and as they age they probably take even more.
If your truck doesn’t have a horn relay, now would be the time to add one.

Not sure where your other fusible links are. But if you’re not messing with that particular wire, you might leave them for now.

 

The fusible links are being removed with their respective cabling because the cabling is far too corroded to save. The whole harness is compromised between corrosion and previous owner.

I haven't seen any AWG # markings on any of the cables in this truck. As far as cable sizing goes I made edumacated guesses, sometimes the insulation can be misleading a make a cable look larger or smaller if the cable isn't stamped. What I assumed to be 10 or 8 gauge ( the BLK/YLW cable for example) have been replaced with #6 marine grade. The smaller wires that appear to be either 16# or 18# have been replaced with 10# so far. My plan for replacing cables was to upsize everything anyway to help the system breathe easier and future proof incase more components get added later.

Some of the new fuses will be ANL and some will probably be MIDI, I need to sit down and determine that part depending on the load and duration of the circuit device.

No existing horn relay, will be installed later, need horns as well. Those GEP boxes look like a good candidate for housing the relay.

Are the fusible links Ford used Tin, Copper, Aluminum or Iron?

 

No idea. The subject has never come up that I have seen at least. I would assume copper, though, since they are bonded to copper stranded wire.
Maybe the others know if that makes sense or not.

 

Well you just opened up another rabbit hole. Copper clad aluminum, aluminum clad copper? Tin clad copper?

 

Are those options for fusible links that you're finding? Or are they options for fuse holders, solder, or other components that you're trying to match up?

And you're certainly over-killing the gauge sizes. Sometimes I'm a big fan of overkilling wiring. Such as battery cables, charge cables, and main power feeds.
But for standard load circuits, you don't need to make your life miserable by adding 10ga wire where you don't need to. This makes it harder to route, bend, solder and connect things when they are just using a light load in the first place.
But if you've got the space, patience and aesthetic where larger than normal wires will not bother you, might as well future-proof, as you were saying. I'll just add to make sure you need to future-proof every circuit. After all, a heater motor pulls a good load, but will anything else be added to that wire? Maybe, maybe not.
A radio uses just a few amps, and upgrading to a pumped up blaring stereo is likely to use a different power source anyway.
Just pointing out things you might not need to up-size so much.

No idea on the base materials however. Good luck on that.

Have fun!

Paul

 

I have several reasons for oversizing all conductors, so far the routing and space has been a non issue since we have so much room in these old trucks. I'm not strictly doing 6# and 10# I did 1/0 for my battery cables and starter, I'm kinda looking at it as what was it doing before, what I think the size is and what may happen. For the lighting I went with 10# because the factory lighting circuits looked like 16# which has probably caused many people a lot of heartache over the years. I plan on adding more to that lighting circuit specifically, thus the 10#, I'm still amazed at that much power over that much #16 wire on a DC load. I've heard a story or two about tail lights catching fire on these old trucks. For sensors and inputs with nominal 0-3vdc like the sending units, looks like the same deal with the 16# for that I would probably bump up to 14#.

Yeah without knowing what metal combination of link Ford used its seems kinda like a guessing game when it comes to replacing links as well?

We don't generally solder in the electrical industry anymore, everybody has moved away from soldering to crimp or compression type connectors. Plumbers as well I believe.