Kubota B6000 charging system

[Oldie68]

Hi all, new here.
Recrntly acquired a B6000 with a fel and a backhoe.
Found fan-belt had been replaced but somebody didn't reinstall the tensioner.
When I figured this out and sort of got some tension on the belt, I see from motor running charging system doesnt seem to be working.
Only 11 volts at battery terminals.
Need some help in troubleshooting.
I have 2 downloaded and printed manuals. Operators and service.
Not overly descriptive or easily illustrated.

 

[Vigo327]

There are two wires coming out from behind the central pulley on the front of the engine. Put a multimeter on ac voltage, unhook those wires from the harness and hook the meter leads to them. Polarity doesn't matter. When the engine is running, you should be able to get 13+ volts out of it, although perhaps not at idle. This AC voltage has to be higher than the battery voltage because the regulator doesn't increase it, it just rectifies it from AC to DC.

So if you can get AC voltage higher than 12.6v out of those two wires, then you can move on to the wiring between there and the regulator, the regulator itself, and wiring from the regulator to the battery.

 

[Oldie68]

There are two wires coming out from behind the central pulley on the front of the engine. Put a multimeter on ac voltage, unhook those wires from the harness and hook the meter leads to them. Polarity doesn't matter. When the engine is running, you should be able to get 13+ volts out of it, although perhaps not at idle. This AC voltage has to be higher than the battery voltage because the regulator doesn't increase it, it just rectifies it from AC to DC.

So if you can get AC voltage higher than 12.6v out of those two wires, then you can move on to the wiring between there and the regulator, the regulator itself, and wiring from the regulator to the battery.

OK, I did this I got between 2-3 maybe 4 V AC on the 50 volt scale (not good at reading those analog meters), no matter which way I connected two of three wires to meter.

 

[Vigo327]

If you are measuring at the correct wires then that would indicate that either the stator windings, or perhaps some magnets inside that pulley, have a problem. Another thing you could do is test each of those two wires for a short to ground. Put the meter on ohms and poke one meter lead to the engine block, or battery negative if you can reach it, and the other meter lead to one of the wires coming out from behind the central pulley. The reading should be very high (many thousands of ohms), and it should be about the same on both wires since really they are just the two ends of one long piece of wire called the stator winding. IF you get a low resistance reading, that means that there's been some kind of failure of the insulation of the stator winding and it would DEFINITELY need to be replaced. That would be a smoking gun. If you don't get low resistance to ground, it may still be that the stator winding needs to be replaced, but it's not a certain thing until you verify that whatever magnet(s) are made into the pulley are still present there. I haven't seen the backside of that Kubota pulley yet, but i have seen a fair number of riding mower engine flywheels where the magnets are simply glued into place and overheating the engine can cause them to dislodge, crack/shatter into small shards when they hit something, and then basically 'go missing'.