Charging Issue Kubota B9200

[npalen]

I installed a new regulator about three years ago along with a new battery and new alternator (Kubota calls it a dynamo) just recently on my B9200. Still not charging as evidenced by the battery gradually discharging after quite a few starts. Have checked and don't show any draw when the ignition switch is off using an amp meter.
Any suggestions?

 

[Spanner]

What is the voltage shown across the battery terminals when engine is running at fast idle? (Use your VOM).

:wrench:

 

[npalen]

I was seeing about 11.3 volts yesterday.

 

[Spanner]

You need to be seeing approx. 14.4V

There may be a failure in the wiring from Dynamo to battery via the regulator or in the regulator itself. I don't have a schematic. The wire may lead from the alternator via the regulator to the starter solenoid terminal thus to the battery.

:wrench:

 

[Coyote machine]

As Spanner stated, you're running off battery state of charge. No charging system input back to your battery. If you keep running it this way you will soon kill your battery. Batteries are meant to go between 100% charged to a low of around 80%. Anything lower and the life of the battery is compromised and shortened greatly.
You need to find out what has dropped off in your charging system, alternator output or regulator.

 

[moship]

You can check the dynamo by checking the AC voltage across the two leads coming from the dynamo. No longer have the repair manual to give you the exact specs, but recall the voltage should be 20 volts AC or higher at high rpm. If the dynamo has an AC output, I'd investigate wiring and regulator.

 

[npalen]

Here are the schematics for the wiring diagram and the regulator. They are high resolution so should be able to zoom in.
I was getting in the area of 13 to 14 VDC at high idle a couple months ago after installing a new battery. The old battery had failed at less than a year old.
I am curious what the "1.25" designation is that is shown on some of the connections on the regulator. Does that designate a wire size?
Help is very much appreciated.

 

[Spanner]

Good diagrams, thanks.

Relative wire sizes - Yes.

As MOSHIP describes, check output from Dynamo using VOM at the 2-pin connector. You are looking for AC voltage.

Then check voltage (DC) at the White wire output from the regulator. You need to check both sides of the 6-pin connector plug as there may be a problem at the terminals here. Even worth separating the connector and checking the terminals for corrosion etc.

:wrench:

 

[Coyote machine]

Here are the schematics for the wiring diagram and the regulator. They are high resolution so should be able to zoom in.
I was getting in the area of 13 to 14 VDC at high idle a couple months ago after installing a new battery. The old battery had failed at less than a year old.
I am curious what the "1.25" designation is that is shown on some of the connections on the regulator. Does that designate a wire size?
Help is very much appreciated.

The new battery and the charging system might have been working then, but whenever whatever went wrong the battery clearly isn't getting more input than it's putting out; which is what is required to keep the battery working as designed. Not that I'm telling you anything you don't know already, but sometimes it seems like a new battery has solved a problem that still exists and can mislead one to think whatever was wrong has been solved. Undoubtedly, your new battery could be compromised now depending on how long its been used with the malfunctioning charging system. Just so you know. Once you solve the charging system problem you can then test your relatively new battery for specific gravity in each cell and do a load test, AFTER it has been charged fully and allowed to sit to reach equilibrium. At that point you'll know what state it is in.

 

[npalen]

Good diagrams, thanks.

Relative wire sizes - Yes.

As MOSHIP describes, check output from Dynamo using VOM at the 2-pin connector. You are looking for AC voltage.

Then check voltage (DC) at the White wire output from the regulator. You need to check both sides of the 6-pin connector plug as there may be a problem at the terminals here. Even worth separating the connector and checking the terminals for corrosion etc.

:wrench:

Eureka!

I checked and found the correct AC voltage from the dynamo at the harness 6-pin connector plug so I was going to order a new voltage regulator. But then went back and read your post again about checking the terminals inside the connector. So then checked for the voltage on the regulator side of the connector and wasn't getting a reading.

Had a devil of a time getting the connector apart and then found that one of the terminals from the dynamo had been damaged apparently when I installed the new regulator a couple years ago. It was not making a good connection and the resulting heat from the 40 VAC output of the dynamo with the bad connection had melted the plastic inside the connector.

I replaced the connector with insulated spade terminals and now all is good. Made a wiring diagram so if ever have to replace the regulator will know the connections color code. (The replacement regulator wire colors don't match up with the harness connector colors)

I am curious what the wire designation Sb means in the voltage regulator diagram above. These are the two dynamo wires and they are actually a solid gray color. Makes we wonder if Sb is metric for gray?

Many thanks to all of you guys for walking me thru this!