Battery fuse box melting. Replaced and new one melts too??

I replaced my battery fuse box about a year ago because it had melted and was having issues turning in and other electronic issues. Now the new box is also melted. I've cleaned ground and positive wires, fuse contacts, etc. Black wire from alternator gets VERY hot. I replaced that wire with a thicker wire and still same issue. The terminal on black wire that connects to fuse box gets corroded with green stuff even after I clean it within days it gets corroded again and the actual terminal looks like the heat is damaging it. I've followed instructions I've seen here and other sources but noting seems to correct the issue of why this wire gets so damn hot. Anyone out there have an idea? Thanks

alexgmzz1 said:

I replaced my battery fuse box about a year ago because it had melted and was having issues turning in and other electronic issues. Now the new box is also melted. I've cleaned ground and positive wires, fuse contacts, etc. Black wire from alternator gets VERY hot. I replaced that wire with a thicker wire and still same issue. The terminal on black wire that connects to fuse box gets corroded with green stuff even after I clean it within days it gets corroded again and the actual terminal looks like the heat is damaging it. I've followed instructions I've seen here and other sources but noting seems to correct the issue of why this wire gets so damn hot. Anyone out there have an idea? Thanks

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Replace wire from alternator to fuse box. It most likely has too much resistance.

Get the 4 gauge replacement. http://innovativewiring.com/?page_id=161

Green is copper as it corrodes. What kind of battery do you have? Could be out gassing too much? Do you know how to do voltage drops? That will help you track down exactly where the problem(s) is instead of just randomly doing repairs and hoping you fixed it.

Just went through this on a 02 Jetta I bought as my daily beater. Turns out there was a poor crimp connection in the alternator harness at the fuse panel and corrosion on the fuse. Sweated solder into that connection and buffed the mating surfaces (dremel and abrasive disc). Went from 450mV drop to 120mV drop. Cheap fix with tools on hand.

Jason

Jokila I did replace the black wire that comes from alternator with a thicker cable. Are you saying that the thicker cable may have too much resistance and I should replace it again with a thinner cable?

Jason I have a Duracell battery. Now the car won't start. No power and no crank. All lights off - no dash lights no clock just no power. I jumped it and nothing. I got a new battery and nothing. The only light is the light on my car charger connected to cigarette lighter and it's very dim. I don't know how to do a volt drop. Easy to follow steps?

It sounds like one of the big wires or main grounds. When a wire is too small it tries to provide the same current and can't, the result is heat. An old damaged wire becomes "too small" as it looses material. You can check with a good ohm meter, take the wire out of circuit, calculate the resistance, compare to the actual. Usually you can see where the issue is, but not always. I would check all the big stuff and fuses and connecters.

Short explanation for voltage drop - set volt meter to DC, lower setting (IE:2V) since you are looking for very small amounts. Red and black don't matter for this test. Touch one lead before suspect connection, one lead after, both on the same side of circuit.

Here is an example. Touch red lead to battery post, black lead to battery clamp. Should be 0 or very close, unless you have a badly corroded clamp. Keep the red lead on battery post and start moving further down the circuit (like to the cable from the fuse panel, then to the fuse panel, then each side of the fuse, etc.). Also you need a load on the circuit such as engine running with the A/C, defroster, lights, etc. Spec for alternator harness is vague, but I like to keep it 200mV or less. Also ground side should be 100mV or less.

Sounds like you may have a cable crimp that came loose. Check big grounds and positives, mainly around the battery.

Jason

alexgmzz1 said:

Jokila I did replace the black wire that comes from alternator with a thicker cable. Are you saying that the thicker cable may have too much resistance and I should replace it again with a thinner cable?

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Something is wrong with that wire if it is getting hot. Too much resistance. Bigger should mean better, but you need to follow the other's advice to trace down the issue.

Do you have amplifiers or other items that use a lot of power?

double post................

Sometimes cable will corrode under the insulation. Cut back the insulation on the wire some were near wear it gets hot and look for green corrosion on the copper. Also look for green corrosion underneath the crimps.

A volt meter will not tell you much unless you understand how to use it. A simpler way is to look for were there is heat melting things and work from there for corrosion under the insulation and crimps and for loose connections.

^^^ Exactly!

Visual inspections aren't enough.

When I was a youngster I recall opening up a starter's power cable and finding it a nice green (lots of powder)! BTW - It wasn't my car

Have we checked the fans? I had some crappy ones melting **** from pulling too much power. Finally got me a good set and a spare set.


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