shuts off when jumper cables removed

k0ua · Oct 1, 2013

chip6700 said:
the tractor only has about 100 hours on it. the battery connections are perfectly clean and there appears to be no corrosion anywhere. i had been bushhogging and had finished and was blowing the tractor off over by my shed and when i tried to start it to put it away, it wouldn't start. so maybe that's the answer, the alternator is bad and wasn't charging. as long as it was running i was ok, which would explain why it will jump but not keep running. i guess i find it hard to believe the alternator would go bad so soon.
thanks for all of the good advice, i will try getting a good battery in there and testing the alternator output.

Chip please let us know what you find out. Thanks.

James K0UA

chip6700 · Oct 1, 2013

kubota wants $289 for a new dynamo, i'm going to ask if anyone knows a subsitute for it

k0ua · Oct 1, 2013

Do you have a starter/generator shop in your town? they can be rebuilt pretty easily by those types of folks. Also most auto parts sales, have the ability to test alternators. I would find out for sure what is wrong. before I shelled out the cash.

Soundguy · Oct 1, 2013

i'd throw a generic one on. if a 10si delco is too big.. look at a cs 130 or a hitachi.. those are favorites of antique tractor people that need small diameter alts to repalce small bbl gennies etc. where large 10si models won't fit.

Soundguy · Oct 1, 2013

ps.. keep in mind you will liekly hav to mod the wire system a bit. ie.. if that dynamo uses an external rectifier / regulator pack.. you will need to wire PAST that.. etc.

catfishdaddyengineering · Oct 1, 2013

Was the battery still connected when you had the jumper cables connected and then it died when you removed the jumpers? If so, try what someone above suggested using the car's battery. The tractor battery could have an internal short that is causing the tractor to die after you remove the jumpers. Unless there is a short in the system, alternators will keep the tractor running even if you remove the battery connection.

chip6700 · Oct 1, 2013

yes, the battery was connected and all connections look brand new. the guy at the kubota dealer told me to test the output from the two wires on the dynamo and that they should register 40-60 volts AC. i'll probably have to wait until the weekend to work on it though.

catfishdaddyengineering · Oct 1, 2013

Sounds like the battery has an internal short. I had the same thing happen to a co-worker. He left work in his vehicle, stopped to get supper, and his car would not crank. He called me to come jump him off. His car would crank but die after removing jumpers. We jumped him off but disconnected the positive(+) battery cable this time, and it stayed cranked after removing the jumpers. He drove to Autozone and got a new battery. No problems after that.

Good Luck!

RaydaKub · Oct 1, 2013

I could understand why a car would stop with the short and ignition being too much load for the alternator at low rpm. But a tractor with only 100 hours on it sounds like it would be new enough that it would have a fuel shutoff solenoid that would only be energized when you turn the key off. It would normally NOT be energized. Did I miss something???