YM 2000 Electrical Problem - Battery post melting

[drumwire-HT]

Hi All,

I know little to nothing about electrical issues and need some input. The other day I was running a 4' rotary cutter on my YM 2000 for about an hour and a half when I shut the tractor down to take a break. I came back, turned the key and NOTHING . . . not even a click. The battery is about 6 months old and has shown no signs of fatigue or corrosion to date. Normally, the tractor fires up immediately.

So, I got down and with the key in the OFF position and checked battery cables, only to find the positive post slightly melted -- maybe about 1/6th of the post had melted away on one side (again it was the positive battery post's soft metal melting, not the cable or connector to the battery cable). I immediately removed the positive wire from the post for fear of the battery exploding and experienced excessive sparking while removing it (again key was in off position). I looked at the wires to the starter, alternator, and ignition but didn't notice anything melted, pulled away, broken, or otherwise out of the ordinary that would reveal a short (granted I did not trace them carefully). The positive terminal that connects to the battery had a little rust on the metal connector attached to the cable (like always) but nothing new or excessive. I don't think it is corrosion at the terminal. The post was clean as a whistle, except for drips of metal from the slightly melted post. I felt of the starter, and it was extremely hot to the touch.

So, I let it cool off over night, came back today to try again and when connecting the positive post to the battery (key in off position) got excessive sparking / beginning to melt the post gain immediately. So, same problem / no change. I had hoped starter hung up and got too hot and by chance might start, but no luck. Let me also say that this is the first time I've had any issues with the tractor failing to start or turn over. This came as a complete surprise. It has a Denso or Danso starter from Japan on it with a Yanmar label, but I'm not sure if this is the original. I realize starters can be rebuilt and solenoids can be replaced, but at $100 for a starter I'll just replace it. But . . . I'm thinking there has to be a short somewhere (melted wire / hidden corrosion in the cabling / cut cable), or the starter or solenoid is bad. I'm doubtful it is the switch itself, but what do I know? Thoughts?

Again, I'm not much of a mechanic. So, if you have other ideas or I'm overlooking something I'd appreciate your input.

Thanks!

 

[Aaron-HT]

In order for the battery terminal to melt like that there has to be a problem with one of the main power wires (any smaller wire would just melt). That makes troubleshooting easy since the main power wire is only a few feet long (goes from battery + terminal to starter solenoid). Try disconnecting the main power wire from the starter & see if you still get sparks. If yes then there is a short in the wire from the battery to the starter. If no sparks then the starter is causing the excessive draw. Try removing the small wire from the solenoid to be sure the ignition switch was not stuck (internally or externally) in the 'start' position. If you still get sparks with the small solenoid wire disconnected then it is time to get the starter checked or replaced.

 

[Norm-HT]

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Check the battery connection on the starter for a short with the starter case.

 

[drumwire-HT]

Thank you all! I actually found a hidden short right in front of my face right after posting this and just now came back to check responses (sorry for the delay). The positive cable somehow got jammed against the battery case and was cut. I didn't notice it because it looked normal, but upon very close inspection / trace back from the positive terminal I saw it. Apparently something like a limb penetrated the opening in the hood / front grill and pressed against the battery and drove the cable / battery back into the box. So it resulted in the positive wire grounded to the frame. Problem solved with a little electrical tape. You guys were right on it, and thanks again for the reply!