JD 750 new battery short

[wbakunis]

Hello, today a family friend asked me to look at their JD750. They bought a new 12v battery and installed it. Wiring immediately started smoking. I Spent the day looking for faults. I found that the small white wire leading off the starter to the key switch was broken. I replaced that wire leaving one end unhooked. I quickly touched the new wire to the wire leading up the keyswitch. Wires got hot very fast. It's almost as if the new battery is way too strong for the tractor. It's the same battery that was in it previously. Previous battery stopped holding a charge. I have no clue what is wrong. The fuses are still good. None have blown.

 

[atsah]

12v is 12v, the battery isn't too strong, you have a short some where.. Maybe in the switch.. I am surprised you didn't blow a fuse though..

 

[void777]

wbakunis

check the ground to the frame that's what heats up the white wire to the starter on my yanmar ?

 

[jd110]

Definitely sounds like a short, but another thing to check, are you sure battery is connected properly? Negative should go to ground and positive to the starter. WIth the key turned off, the wire should not spark or get hot. If it does I suspect the key switch is defective.

 

[Rock knocker]

I looked at all three of my 850-950-1050 diagrams, and am going to assume that the 750 is the same. The white wire hits three seperate locations: the battery via the starter lug, the "A" lug on the alternator, and acts as the unfused feed to the key switch (center or "B" terminal) with the fuses downstream of the key.

A ground to frame in the wire, a bad switch or a short in the alternator are all equally likely. That said, I would first pull the "A" plug from the alternator and then proceed as before. If the alternator is bad, you should be able to safely start and run the machine. You will only lack charging, but the current pull of these machines is small. Electricity is only needed to run the starter, the lights and the oil pressure and temp warnings. Run without lights in the day time and it will run for a long time.

 

[Coyote machine]

Hello, today a family friend asked me to look at their JD750. They bought a new 12v battery and installed it. Wiring immediately started smoking. I Spent the day looking for faults. I found that the small white wire leading off the starter to the key switch was broken. I replaced that wire leaving one end unhooked. I quickly touched the new wire to the wire leading up the keyswitch. Wires got hot very fast. It's almost as if the new battery is way too strong for the tractor. It's the same battery that was in it previously. Previous battery stopped holding a charge. I have no clue what is wrong. The fuses are still good. None have blown.

Not sure what the owner's sequence of prior events was BEFORE he bought a new battery. What is your understanding, in as much detail as you have? Was the tractor not starting and then he would put a charger on the battery? Trickle or larger? What does he/you mean the 'previous battery stopped holding a charge'? Was that battery ever removed and tested by a shop or store?
Was the 'white wire' broken as in it broke in two, or did it show signs of being chewed?
Is the tractor stored inside or out, and are rodents a factor?
Can the ignition switch be removed from where it's located to inspect the wiring?

 

[wbakunis]

I looked at all three of my 850-950-1050 diagrams, and am going to assume that the 750 is the same. The white wire hits three seperate locations: the battery via the starter lug, the "A" lug on the alternator, and acts as the unfused feed to the key switch (center or "B" terminal) with the fuses downstream of the key.

A ground to frame in the wire, a bad switch or a short in the alternator are all equally likely. That said, I would first pull the "A" plug from the alternator and then proceed as before. If the alternator is bad, you should be able to safely start and run the machine. You will only lack charging, but the current pull of these machines is small. Electricity is only needed to run the starter, the lights and the oil pressure and temp warnings. Run without lights in the day time and it will run for a long time.

Ok, i pulled the plug from alternator. Tried touching the white wires back together. Wires got hot quickly again.

Not sure what the owner's sequence of prior events was BEFORE he bought a new battery. What is your understanding, in as much detail as you have? Was the tractor not starting and then he would put a charger on the battery? Trickle or larger? What does he/you mean the 'previous battery stopped holding a charge'? Was that battery ever removed and tested by a shop or store?
Was the 'white wire' broken as in it broke in two, or did it show signs of being chewed?
Is the tractor stored inside or out, and are rodents a factor?
Can the ignition switch be removed from where it's located to inspect the wiring?

Machine has been used just under 1560 hours. They dont know how well first owner maintained it. Friend has kept it outside next to the barn for the last year or so. Was used a couple times when they noticed it wasn't charging. Kept having to hook the battery up to a booster when starting. Rodents are a considerable factor. I removed the dash yesterday to check wiring and found a mouse house. Wiring was not chewed luckily. Plastic wiring sleeve was still intact.

 

[Coyote machine]

What about ignition wires, have you inspected them at the switch. Mice chew, it's their thing. Look everywhere....

 

[wbakunis]

saw nothing chewed. If anything, the mouse house really held in lots of moisture. Everything under the dash was wet to a degree.

 

[Industrial Toys]

Lucky nothing burned down. By now, I would have stopped touching the wires long ago and put maybe an old headlight in the circuit to determine a shorted condition, until the fault is found.