MonteMack Posted December 19, 2020 Share Posted December 19, 2020 Hey question for any electrical gurus out there, wiring up my new hei engine harness from american auto wire, i was an idiot and forgot to disconnect the battery when putting the power cable on the back of the alternator. It sparked and i think it shorted something out. I dont have a junction block or horn relay etc and the only fusible link i believe is this red one coming off the starter solenoid top post... Hoping replacing the fusible link wire will fix the issue. Thanks for any advice! Snapchat-967071858.mp4 Snapchat-967071858.mp4 Quote Link to comment Share on other sites More sharing options...
wallaby Posted December 19, 2020 Share Posted December 19, 2020 Not sure how American does their system. You have a big cable from the battery to the starter to feed the starter when it's being used. The stock system then branches off from that same terminal on the starter with another wire that is used to feed the rest of the car. The wire used to feed the car could be connected there at the starter, or at the other end of the cable at the battery..either way is correct electrically. And yes, the circuit is protected with a fusible link to prevent a meltdown if a direct short should occur. I would guess that you blew the fusible link. You probably have electricity down to the starter, but then it goes no further. A fusible link is very flexible with a rubber insulation, and it will burn the conductor inside when it blows, without burning through the insulation. So what you end up with is a wire that LOOKS ok, but won't pass any electricity through it anymore. You can stab it with a test probe to verify it's blown, or sometimes you can feel it with your fingers as you try to bend it...if its blown you may feel an area along its length that feels stiff or rigid where the conductors have welded themselves together near the place where it eventually burned in two. The flex test with your fingers doesn't always reveal anything, but it might. To replace the link, you need to cut out the entire old link back to the regular wire, and replace it with a same length piece of fusible link wire of the same color. The auto parts store has fusible link wire in like 2 foot coils available in different colors. The color of the wire indicates the amperage of the fuse. Don't try to repair a blown fusible link with a splice in the middle somewhere. You will find that inside the fusible wire there are only a few strands of wire, and butt connectors that fit the surrounding wires are too big to secure to the tiny fuse link wire. I make fusible links on the bench and solder non-insulated butt connectors (or ring terminals as required) to each end of the link, then take it to the car where it can be crimped in place then wrapped with tape, or shrink tube. Once you fix it, it will probably never give you trouble again, but while I'm at the bench and have extra wire I make a spare and chuck it in my glovebox. I'm not sure if newer cars use fusible links any more. They use standard wire to hook up a maxi fuse to protect the circuit instead. The maxi fuse is much easier to diagnose and replace. The neat thing about a fusible link is that they can handle power surges without blowing...kind of like a "slow blow" fuse. Perfect for an electric fan perhaps, where high current at startup would blow a standard fuse. 1 Quote Link to comment Share on other sites More sharing options...
71MonteCarloMD Posted December 27, 2020 Share Posted December 27, 2020 @wallaby can you share pictures of what you did as I probably will need to do this on my sons 1972 GMC? Quote Link to comment Share on other sites More sharing options...
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