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relocating battery to trunk, fusible link?

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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.     

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  • 3 weeks later...

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.


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.

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  • 2 months later...

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!

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