Fusible link questions

[Jeff]

My car is a 1970 Fury. The FSM calls for a fusible link between the positive terminal on the battery and the starter relay. See picture below. Instead of that, there is a section of garden hose around a terribly degraded piece of wire. I want to put it back to original. Does anyone have a picture that shows where the fusible link should be located and the connectors? How do I know what fusible link to get?

Any guesses on why the garden hose was installed? I'm a little nervous about putting it back to original. Obviously something was going haywire.

 

[Polara_500]

I'd guess he was wanting to use a piece of wire he had laying around from something else but it had damaged insulation so the garden hose was to serve as the insulation, (which would probably work in a 12v application). Basically a cheapo temporary fix that lasted way too long. I don't have any good photos of a comparable setup so can't help with that.

 

[70Tom]

See if you can find any good pics of it in Critter's thread on his 70. I can take one when I get home (provided I remember to do so) if no one else can help out earlier than that.

https://www.forcbodiesonly.com/mopa...rs-other-mistress-1970-plymouth-fury-3.27753/

 

[live4theking]

Garden hose = hill billy insulation.

 

[Jeff]

Garden hose = hill billy insulation.

Lol, it came off a farm in Idaho. You should have seen the trailer hitch. One of these days I will put pics of all the examples of farm engineering on one thread.

 

[Jeff]

See if you can find any good pics of it in Critter's thread on his 70. I can take one when I get home (provided I remember to do so) if no one else can help out earlier than that.

https://www.forcbodiesonly.com/mopa...rs-other-mistress-1970-plymouth-fury-3.27753/

Great tip! It is shown on this picture from Critter's thread. Now I just need to find the right connectors and fusible link.

 

[saylor]

HEY THERES A GARDEN HOSE IN YOUR ENGINE COMPARTMENT!

o -

you need 14ga and 16ga links. there is some calculable ratio - maybe 4x the wire you are protecting or something, I forget.

but ya, 14 and 16. there are 2 links down in there somewhere under that hose.


try not to die -

- saylor

 

[Jeff]

I found a NOS fusible link, but per the parts book, it is for cars with a 60 amp alternator (which is weird because the FSM says they come in 34.5, 44.5, and 51 amp versions). From reading about fusible links on C and B bodies, it seems like it should be OK to use that on my car, even if I have a lower amp alternator. Any thoughts on that?

 

[MrMoparCHP]

I found a NOS fusible link, but per the parts book, it is for cars with a 60 amp alternator (which is weird because the FSM says they come in 34.5, 44.5, and 51 amp versions). From reading about fusible links on C and B bodies, it seems like it should be OK to use that on my car, even if I have a lower amp alternator. Any thoughts on that?

What color is it? Part number?

I may have the correct NOS one for you, I need the correct 60 amp one.


Alan

 

[Fury440]

I took a look at my car and took some pictures.
The large cable from the battery +ve routed to a battery cutoff switch mounted under the fend lip out of the way. From the switch two cables, big fat mama goes to the starter motor, the skinny one is a #10 feed for all the car's circuits. The key is attached to a "red power looking wire" and if I shut the power off I can drop the key down under the fender where a crook is unlikely to find. Rather than take the key with me, I attached it to the car so some idiot at a car show wouldn't turn it off and take the key leaving me high and dry.

The two cables run along the inner wheel well with the big mama going directly to the starter motor and the #10 to a female push on connector. The fusible link has male connector at both ends. from the fusible link the #10 cable continues on to the starter relay.

Finally to the starter relay. Note also my lack of water shields over the starter relay and the bulkhead connector. If I run across shields I'll install them, but it's not a big deal.

A word about fusible links. A fusible link does not protect individual loads, it protects the wire it's wired into. The fusible link is not rated in amps like a fuse, it's rated for the wire gauge being protected. Basically it's a short piece of wire one or two gauge size smaller than the wire being protected. When the amps get high enough to damage or set fire to your wiring harness, the link burns and breaks the circuit. The jacket on the fusible link is rated for high temp so when the link burns out, the jacket still protects the car. Your circuit diagram shows the power feed to be a Red #10 and it shows the fusible link to a #14 which is two gauges smaller than #10. When you buy your fusible link, buy two, one for the car and one for the glove box.

Hope all this makes sense.

 

[Fury440]

I should add that it doesn't matter how big your alternator is, the limiting factor is always the gauge of wire actually used in your wiring harness. I read many posts from people who install huge alternators, but use the factory harness and very carefully install huge fusible links. Then they can't understand why their "must be defective" fusible link didn't blow before the wiring harness went up in smoke. If you must have a monster alternator, run a fat charge wire directly to the battery and run all high load devices using relays wired directly to the battery. Note all those wires running directly to the battery should each have it's own fusible link.

 

[Big_John]

HEY THERES A GARDEN HOSE IN YOUR ENGINE COMPARTMENT!

o -

you need 14ga and 16ga links. there is some calculable ratio - maybe 4x the wire you are protecting or something, I forget.

but ya, 14 and 16. there are 2 links down in there somewhere under that hose.


try not to die -

- saylor

The fusible link needs to be 4 gauge numbers smaller than the wire you are protecting. Example #10 wire needs a #14 fusible link. It also needs to be 9" long maximum.

 

[Fury440]

The fusible link needs to be 4 gauge numbers smaller than the wire you are protecting. Example #10 wire needs a #14 fusible link. It also needs to be 9" long maximum.

That's actually only 2 because I don't think anyone uses #11 or #13 gauge wires, at least I've never seen them used.

 

[livininharrow]

Lol, it came off a farm in Idaho. You should have seen the trailer hitch. One of these days I will put pics of all the examples of farm engineering on one thread.

most farmers are a great bunch .some of the hardest working people I know. no extra time on their hands, makeshift to get **** going to keep the farm running and feed the family. I repair dairy coolers for dairy farmers in my area and they are some of the most resourceful people I know. they have to be part time mechanics, plumbers, electricians , horticultural and chemical gurus, sometimes a veterinarian when the real vet cant get there when a cow is giving berth and sending their kids off to school. if i forgot something let me know. and I love to see farmer engineering at its best. lol. pics please

 

[Big_John]

That's actually only 2 because I don't think anyone uses #11 or #13 gauge wires, at least I've never seen them used.

Read it again please. Four gauge numbers.

10+4=14

Since you ask.... I don't believe that the #11 and #13 are readily available, but the American Wire Gauge (AWG) standard has been around since 1857. The standard runs from 40 to 0000 (or 4/0) and includes all the numbers, odd and even and that would include #11 and #13.

For another example, #1 wire is available for use as welding cable.


American Wire Gauge

 

[Jeff]

Thanks for all the info and pictures. I understand that fusible link sizing is based on the wire it is on, but when looking for NOS parts you get part numbers and alternator amperage rather than a fusible link gauge number. IE, the parts manual has a particular fusible link for B bodies with a 60 amp alternator and a different number for my car. Maybe the B bodies with the 60 amp alternator have an 8 gauge wire in that location instead of the 10 gauge on mine. From post 11, it sounds like I should avoid using a fusible link for a car with a 60 amp alternator because it might not blow early enough.

On a related note, does anyone know a source for the push on connectors and the wire hold downs circled in the picture below? When I find a fusible link, it will have the male connectors but I will need two female ends to set it up.

 

[Fury440]

I bought those clips ( a full set) from National Moparts for about $25 or so.

 

[Jeff]

What color is it? Part number?

I may have the correct NOS one for you, I need the correct 60 amp one.


Alan

Hi Alan,
I have not seen a picture of it yet so I don't know the color. If I get a picture I will let you know.

I need part number 2889419. The 60 amp one is 2822692. Maybe if I get my hands on the 60 amp one and you have the one I need we can trade?
Jeff

 

[Fury440]

A picture - red with a white stripe

Let me repeat, the size of the fusible link is determined by the wire it is protecting. The capacity of the battery or the power of the alternator is NOT RELEVANT!

Replacing a #14 fusible link with a #12 is like going to your house fuse box and swapping out those pesky 15 Amp fuses that blow when you plug too many things in an outlet and replacing them with 30 Amp fuses. Get out the marshmallows, going to be a great cooking fire.

Read this posting
and
Read this posting.

With electrical power wiring, if you are not sure, don't do it!

I'm sorry if I sound authoritarian, but as an Electrical Engineer with 50 odd years of experience, I've either done it or seen it done. Disrespect electricity and it will bite your butt, if it doesn't just outright kill you first.

 

[Jeff]

I didn't disagree or ignore what you said. It's just that the NOS parts and the parts manual don't identify the gauge. I think I need a # 14 fusible link, but that information is not given for the parts. How do you know if the one pictured is a 12 or a 14? My guess is part number 2889419 is a 14 and part number 2822692 is a 12. That's why I said I should avoid 2822692.