Wire (going to alternator?) from battery getting really hot

[Brett5cent]

Hello,
I ran into a problem a few months ago when driving the van. I got back home and smelt a wire melting, I got it home, disconnected the battery and left it for awhile. When I went to reconnect the battery I immediately smelled it burning again, I was able to start it up, but the whole electric system was very weak and the van died quickly. I replaced the battery and I am getting no start, and a really hot wire coming off the positive. It is not either of the fusible links but the third wire, I hope the picture posts but it’s the one with yellow on the end. Any help is greatly appriciated. Thank you

[Jan-Willem]

Hi,
sorry, I can't make much sense of your picture, as the connections may not be as they came from the factory, and I cannot compare it to my van, as I am sure it is not how it came from the factory :lol:
But yes, there is a thin cable, from the positive terminal of the battery, that, when it came from the factory, had a little fuse in a yellow holder, right next to the battery. Mine was a green cable on the battery end. This cable goes to the control plug on the alternator, to the top pin, the Sense pin. The alternator uses this wire to sense the voltage in the battery. This cable is unswitched, always connected to the alternator.
However, if this is indeed the cable, then maybe the fuse is missing? I would expect the fuse to blow before the wire gets hot.
But it is easy enough to check this cable. You can unplug it from the alternator, and disconnect it from the battery, then use a multimeter, to check continuity, and also check continuity to the ground (which should be there, if it is, the wire is shorted, probably where it passes through a hole through the body)
If you cannot reach the plug in the alternator, or it seems fragile, you can follow the wire, there is a another connector, which is a lot easier to unplug.
The sense wire, is the white wire, I think.
Jan-Willem

[Brett5cent]

Hi, just a follow up. After further investigation I’ve concluded that the diodes on alternator went bad, causing current to flow from the battery to the alternator when connected to the battery. Alternator was getting really hot with the engine not running and cold, and after doing a bench test, it appears that this is in fact my issue. I’ll be replacing the alternator in the next couple days and follow up with a 100% answer that this was it. Thank you.

[Brett5cent]

Also, the no start issue has been an intermittent problem for awhile. I pulled my starter and replaced contacts and plunger inside, this has fixed that issue (which was a separate issue in itself. Just to not confuse anyone.

[Brett5cent]

100%confirmed, bad alternator!