3 brush generator

1 - Remove the cover off the regulator and find the regulator relay - it's the one whose contacts are held CLOSED by spring tension.

2 - Connect an accurate voltmeter across the battery terminals.

3 - Start the tractor and run it at max RPM.

4 - While observing the voltmeter, gently bend the spring hanger on the regulator relay to INCREASE spring tension. Stop when the voltmeter reads between 9.6 and 9.8 volts. Be careful here! The relay is very sensitive to spring tension - it's easy to increase it too much.

Note: If your tractor has just a cutout relay - identified by a 4-position (L-H-D-B) light switch, there is no way to adjust voltage other than by messing with the 3rd brush as previously discussed.

6 volt: 7.2 - 7.4 volts
8 volt: 9.6 - 9.8
12 volt: 14.4 - 14.8

Also make sure you don't exceed generator current rating at full RPM (13 - 15 amps for a letter series Farmall) so you don't overheat the generator.

Above settings are for cool weather. If temps are routinely 80 deg and above, drop the voltages by a few tenths to improve battery life.

Note - You CAN replace the cutout with a voltage regulator. Requires a bit of additional wiring, but does a better job of regulating than a cutout/LHDB light switch combination - especially in the hands of an inexperienced operator. I recently helped a friend replace the cutout with a regulator on his '50 H, then reset it to accommodate the 8 bolt battery. It's working great.

Bob M

Bob M