Fusible Link Gauging
 

Looking to replace a blown FL on my '69 Couoe.
My first attempt will be at the starter power feed.
All literature I can see says to always pick a FL that is gauged 2 sizes smaller than the wire it's protecting.
Just to be clear, does this mean I need a 16 gauge FL for 12 gauge wire? Or a 14 gauge?
Pretty sure they don't gauge wires in odd numbers, so would 2 sizes smaller mean jumpting from 12 to 16? Or 12 to 14?
Also, is the only line protected at the starter, the smaller red 12 gauge that doubles up on the main + battery post? The AIM is not clear, it only shows the FL on the main harness, not on an individual wire. Wiring schemfrom Willcox shows only on the red 12 gauge hot line.
Yhanks.

Good question... 12g wire needs a 16g fuesable link

1 size = 2 gauge
2 sizes = 4 gauge

A true fusible link has several important features:
The wire size is smaller than the main wire feeding it (as noted above);
The link has NON-flammable insulation around the fuse wire; (If it fails, the wire melts and is hot enough to catch the insulation on fire. If the insulation is just stock plastic, it will burn....and so might your CAR!)
The ends of the link have non-flammable terminators so the the heat in the failed link will not catch the adjacent wire insulation on fire.

I have replaced fusible links with wire....but only wire with non-flammable insulation. Then I put a ball of JB Weld [stick/putty] epoxy at the ends of the link.

It would be easier to just buy a replacement link... BUT you need to verify that the one being sold meets the 3 requirements above. Lots of shoddy aftermarket s4i+ out there for you to buy. And if you know what you really need, you can usually find that, too.

You can get fusible links in different sizes at a NAPA store. I added them to my 66 as GM added them in model year 67. Jerry

I believe there are 3 on my 72
Down at the Starter end
Up where the main goes towards the fuse panel
another at the horn relay

I'll double check
M

https://cimg1.ibsrv.net/gimg/www.cor...a7a64b5002.jpg
Those are the only ones I know (more links actually I guess), been several years since I replaced them so I forgot one)
M

Thanks guys.
All buttoned up now.
Turns out it wasn't a blown FL. When I rewired the harness to the starter, I actually reversed the leads that were to the Red and Purple 12 gauges. [Color me embarrassed but not too surprised! ]
I'm lucky I didn't fry the whole shebang!
I still needed a new fusible link though, as I never really found the one at, or near the starter, so I spliced a new one in [16 gauge] with a ring terminal right at the starter stud.
So the only "casualty" of the job, was the stud on the starter that holds the heat shield and bracket to the block. Snapped that puppy off when replacing that shield. Not sure that's a long term problem, if that actually supports the starter at the front end, but I'm not keen on replacing the whole starter just for that stud.
The original FL may be upstream and buried in the taped harness, but I surmised that having another one in-line couldn't hurt.
Thanks for the help and education an usual!

Why not get an inline fuse holder and replace link with an actual fuse? The stud on starter is a bolt that holds starter motor to starter nose. Any old school rebuilder will have a bunch he didn't have the heart to throw out. or 10 bucks on ebay https://www.ebay.com/itm/NEW-THRU-BOLTS-for-DELCO-10-MT-STARTERS-LOT-OF-2-1-with-ext-1-without-ext/143250485104?epid=17002455676&hash=item2 15a64ef70:g:MiUAAOSwEF5c2afXhttps://www.ebay.com/itm/NEW-THRU-BOLTS-for-DELCO-10-MT-STARTERS-LOT-OF-2-1-with-ext-1-without-ext/143250485104?epid=17002455676&hash=item2 15a64ef70:g:MiUAAOSwEF5c2afX

You NEED the front support bracket for the starter. That is what transfers electrical ground to the starter case. Not good that you broke off the stud. You don't have to buy a new starter; but you will have to remove the starter and disassemble until you can get the broken shaft out and replace it. There's not much of a way around doing that.

Many folks have lost (or thrown away) that front bracket, and they then are plagued with "starter" problems when the engine is hot. Solution: install that front support bracket....