Kubota 7100 (Non-HST) not charging battery

[newshb_k]

Hi All,

I have Kubota B7100 (non-HST) which is not charging battery. I have troubleshooted as below:
1. Checked the output voltage of the alternator, and it ranges from 12.4V to ~26V (based on throttle). The alternator is 2 wire Alternator
2. Verified that this voltage is the same as the input to the voltage regulator. (i.e. tested the two cables ends coming from harness (which is connected to the alternator on the other end).
3. Tested the voltage output of the regulator, (red and black wires) and it is 12.4V when idle, and then start dropping when increasing throttle. It never reaches more than 12.4V.

I though it could be bad regulator, so I purchased a new one Regulator, I hooked it up, and it is still the same behavior.

Any ideas what could be wrong.

 

[007kubotaguy]

Be sure your new regulator is bolted down and grounded. Many times people replace them and don't bolt it down during the troubleshooting process.

 

[newshb_k]

Be sure your new regulator is bolted down and grounded. Many times people replace them and don't bolt it down during the troubleshooting process.

I have it bolted, and assured it is grounded. I even connected its black cable to the negative terminal of the battery

 

[North Idaho Wolfman]

Did you test the voltage on the dynamo in AC?

 

[GreensvilleJay]

hmm, can you charge the battery from a regular battery charger, while sitting on the workbench ???
A 'bad' battery can 'load down' the rect/reg unit giving the false impression the rect/reg is bad.

 

[newshb_k]

Did you test the voltage on the dynamo in AC?

Yes, and as mentioned, it varies from 12.4 to ~26

hmm, can you charge the battery from a regular battery charger, while sitting on the workbench ???
A 'bad' battery can 'load down' the rect/reg unit giving the false impression the rect/reg is bad.

I measured the output directly from the regulator (I disconnected the red wire of the regulator and tested output from there)

The battery voltage is 11.98V

 

[newshb_k]

UPDATE: I found out a loose wire (the one going from the motor to the +ve battery, once tightened, it started charging battery.