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melted alternator wire 96 legacy


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the wire that goes from the battery to the alternator has melted. not sure what it is called. looks like all i need to do is re-connect it. alternator is fine. except that this is the second time this has happened in 3 months. anybody have any idea what is going on? i have heard there may be a short. its possible the two wires meet right there and the wire coating has chaffed over time. does anybody know what gauge wire it is so i can just replace it and get back on the road. i can figure out whats ultimately wrong later.

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any large guage wire is good within the same relative size. bigger is generally better as long as size doesn't hinder working with it and end results.

 

once you get it repaired maybe check it for heat - see how hot it feels - though it could be intermittent.

 

replace wire and make sure end connections are absolutely clean and tight. you can strip the old wiring of insulation and you may find significant corrosion all up in the wire strands. it's most likely the end connections are just dirty and not tight.

 

it's like using jumper cables - if you don't have a great clamp/contact the cables get extremely hot very quickly due to basic electrical principles.

Edited by grossgary
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Are you running a lot of aftermarket electronics? Like say 80 amp+ worth of car amplifiers, etc.?

 

I've seen 4 gauge amplifier 12v+ wire get hot enough to start cooking plastic fuse holders as the gauge was too small, and was pulling too much current. In that case, upgrading to something like 2 gauge (or larger) or dual 4 gauge for multiple amplifiers (within reason) and upgrading to separate amp grounds, helped, but if you are pulling enough current to do that, you probably need a beefier alternator as well. I retrofitted a 2011 130 amp Tribeca alt into my 95' Legacy with minor effort and it's going on almost 4 years now, and seems to have a very nice amperage curve.

 

IF you have no aftermarket electrical demands, you might have a failed ground wire (engine to chassis OR chassis to battery) somewhere in the chain, as well as faulty battery connectors, or even something as simple as the charge wire feeding the alt is corroded internally and breaking apart, which would cause more current through the surviving stands + heat until failure.  

 

Years ago I had a 79' Mustang with a 306 retrofit, and the guy that originally made the swap didn't put heavy enough grounds in, which lead to starter-click/ no start, AND it'd cook the 12v+ battery cable while trying to crank. In that case, I was able to jump the engine directly to the chassis (with a metal tire iron no less) while using a remote switch to crank it and it'd fire right up. So I went ahead and several redundant ground straps from engine block to chassis, and replaced the 12v+ feeding the starter and the battery ground. Have to use BARE metal locations and use something to inhibit rust. But after doing that, it never had any other issues. 

 

You can also pop your hood (better if underhood temps are cool as everything will be ambient) crank the engine, shut off, crank again, shut off,  then immediately (carefully as it might very hot) check if your wire is hot or not. If it is hot just from cranking, you have a weak ground, most likely off the battery to the starter.

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