Review on Holdwell 12V Voltage Regulator, Compatible with Kubota Tractor Models: B7100D, B7100HST-D, B7100HSTE, B4200, B5100E, B5100D - Part #15372-64602, 15372-64600 by Samuel Nguyen

This regulator replaced the original regulator on our early 80's Kubota B5100 that failed. I determined that the old regulator had failed by measuring the AC voltage to the old regulator (two blue wires) at 18 volts with the engine running at high idle, so it was clear the alternator was running. The constant voltage on the battery after a full charge was only 12.6 volts, so the regulator did not change the battery. With the new regulator, as the engine returned to high idle, the DC voltage at the battery rose steadily from 13.1 volts.