relocating battery to trunk, fusible link?

[scooter stuff]

so, there is fusible link in my 71' 510 that runs from the harness to the positive terminal. should i run it to the starter? what amperage/guage wire should i run? I tried the search, found nothing.     

[ohmrchristopher]

http://community.ratsun.net/topic/39441-battery-relocation/

 

http://community.ratsun.net/topic/13383-need-help-with-battery-relocation/

[besser]

A Fusible Link is a sacrificial slow burn fuse for the wiring loom. SAE standards stipulate the specs and the first being in 1970. Copper wire is used, the gauge and length determine the burn through time. The wire coating (it has "fusible wire" printed on the outer coating) and end terminals are also specified and special, they will not burn or melt. Colour of the coating is not standardised. The systems designer puts these in to protect your loom from overload to your wiring circuits. Each circuit will have a different requirement for the strength of fusible link.

 

The starter circuit is protected from the starter getting stuck engaged is a good example. The Starter if stuck engaged with the ring gear with generous motor revs would force large amps up the line for a sustained time and kill your loom. The fusible link will melt through to protect this. In a 70's 510 I'm working on I just replaced a burnt out one. The existing one was brown 1mm2 and the replacement wire was black 1mm2! Colour means nothing! I measured the length exactly and made the replacement one exactly the same. I also used nonburn terminals.

 

Proper Replacement:

1. Use proper Fusible link wire
2. Make it the same gauge and length
3. Use proper end terminals

OK so if you have no idea of the original spec for your car, you're stuck with no help but need a solution NOW and happen to have side cutters, crimper and standard terminal ends, then you could follow these hack steps

1. Find the thinnest wire in your circuit
2. Get a fingers length (75mm, 3") of the same wire thickness ( your could cut it out of your loom and resplice the loom together) 
3. Attach terminals to each end of the 3" piece that suit the rest of the circuit. Here it's better to use heavier duty terminals then lighter ones. as these will act as heat sinks to protect the rest of your loom
4. Now cut off all the plastic coating from the wire and terminals. Better not having plastic, then burning the car down from sticky flaming goop if the link blows.
5. Seperate the strands of the exposed copper wire and using side cutters, cut half of them out of the link you've just made.
6. Install in car making sure the link doesnt touch anything except the loom your linking it into.

You now have a link that will blow first. protect your loom and not set fire to your car.

 

If after proper installation the link blows imediatly:

1. The original problem may still exist, check the circuit components to make sure they are poperly opperational!
2. The link is too weak. Remake the link however only cut 1/3 of the strands out.

Notes:

Dont use original fusible link wire/specs on a modified loom. You need to identify the weakest wire and work to that!

Never use a "temporary" fix wire, nail, spanner as a substitute for the fusible link.

The fusible link is designed to MELT COPPER wire through. that means HOT.

Useing "fusible link" wire is like medicine. It needs to be the right one and in the right dose, or you die!

DO NOT RELY ON COATING COLOUR. I dont care what your uncle, corner mechanic, home elec store rep says. If they know it so well then they can show you the 8 releases of the standards starting in 1970 until 2010, the manufacturers specifications and the components suppliers, but then you wouldnt be reading this.

[yellowdatsun]

My post will be a lot simpler:  Most people, including myself, ditch the fusible links when relocating the battery. I've never had a problem.

[datzenmike]

The insulation on a fusible link wire is hypalon, a synthetic rubber resistant to high temps and catching fire.

[besser]

Found out my 510 problem that caused the link to blow. Unfortunatly I found it out on the grid at the track in P4!

The ignition was worn and stuck in the crank position instead of returning to the run position. The starter stayed engaged and was being driven by the engine. As it happened I realised the starter was stuck and went to kill the engine. As I grabbed the key I noticed it stuck in the crank position and turned it back to run. The started disengaged!

 

The link burn time saved me, I just had 1/4 of the field past me and had to play catch up. If I had a static fuse it would have blown imediatly and left me stranded.

 

Now I have to rebuild the ignition barrel, just when I thought I had finished the rebuild!

[ggzilla]

Yes, connect existing Fusible Link to the battery feed (either starter main terminal or remote junction terminal if you have added one).

 

Either way the Fusible Link will still protect the starter solenoid circuit.

[thaibuddie]

Hi, I'm not doing a battery relocation, but with a stock wiring setup I was challenged to figure out what this mystery fusible link at the starter was supposed to be.  With this write-up along with the others linked above I finally understand, and I'm lucky enough to have a great electronics store with a selection of fusible links.  So, my question now is - does anyone know what gauge with the circuit I'm trying to protect is?  It's the white wire at the starter - thanks for the help!

[datzenmike]

The 510 fusible link is RED at the starter lug then there is a white wire from it to the fuse box. Red is 50 amp rated and protects a 14 gauge wire.

 

 

 

 

 

[thaibuddie]

Ok, so I don't have the red fusible link that I should, just a white wire.  I thought is was thicker than 14 gauge but that's just from memory (not with the car right now).  If I follow the guidance of the wikipedia page in one of the previous posts and the instructions printed on the labels of the fusible links at my local shop I guess I will be installing the fusible link in the upper left of the photo below, "18 GA FUSIBLE LINKE FOR 14 GA CIRCUIT" I'm still not really sure about this, so if anyone has anything else to offer please enlighten me

 

[benzo]

@thaibuddie @scooter stuff May be off topic but I replaced the fusible link and went with a MIDI fuse. I'm no electrical specialist. This was something my brother recommened when my Alternator went out and the fusible link did its job and broke to save the wiring. I attached a link if you want to go this route. I went this route as easier for me to get replacement fuses and or replace the fuse. This link may not be correct as I believe I got the 50amp one but believe you can choose different ones for your needs.

 

https://www.amazon.com/dp/B0BMPHYHDD?ref=ppx_yo2ov_dt_b_fed_asin_title

 

Hope you all get it all sorted 

Edited October 9, 2024 by benzo

[Stoffregen Motorsports]

@thaibuddie

 

Rule of thumb - fusible link wires should be sized four sizes (numerically) smaller than the wire they are protecting, so a 10ga wire gets a 14ga fusible link.

 

Here's a problem - wires in Japanese cars don't always have the wire gauge printed on the wire, and if they do, it's in metric wire gauge sizes. If you are lucky enough to be able to locate and read the metric wire gauge size printed on the insulation, great. If not, strip the wire end and measure the copper bundle with a digital caliper to get an approximate size, then convert that to AWG size.

Edited October 9, 2024 by Stoffregen Motorsports

[thaibuddie]

Thank you everyone.  To the best of my ability (dark, late, cramped working space) I was able to confirm that the white wire is 14 gauge as datzenmike said, so I installed the 18 gauge fusible link.  I will look into MIDI fuses after I get some other stuff sorted.

[datzenmike]

The problem with a regular fuse is if there is a voltage or current spike it will blow instantly. Fusible links take 5 to 10 seconds to heat up and melt saving you the problem of replacement. If you get fuses, keep a supply in the glove box