4020 John Deere Split Ground System, 24-Volt The 4020 John Deere diesel tractor has a split ground system, where the starting and charging systems are totally insulated 24 volts. The tractor lights are 12 volts, controlled by the ignition switch. Early models of these tractors used a DC generator, which is in the wiring diagram shown. Late model 4020 tractors use a 24- volt insulated alternator by Motorola. Notice the split ground has “A” battery positive to the frame and the “B” has negative to the frame. There are two independent 12-volt running light circuits on the tractor. One is 12-volt negative and the other 12-volt positive. The ignition switch controls both of these accessory circuits. On one side the lights are 12-volt positive ground and 12-volt negative ground on the other side of the tractor. Should the “B” battery NOT stay charged and the “A” battery remain charged, check for any unwanted rust or corrosion grounds inside the starter. The starter must be totally insulated from the tractor frame. An unwanted ground in the starter will cause the “B” battery to drain through the starter as a rate depending on how bad the rust has caused the ground condition. Te | Li ey | Note: Generator A: is negative and A: is positive. The no charge light is fed by negative potential and goes to positive potential at Az. With the Motorola alternator on later model tractors, the no charge light is the reverse potential to that of the DC generator. ¢ “No Charge” light wire is PINK on tractors with serial numbers 91000 and up. e “No Charge” light resistor is mounted on dash panel near light on tractors with serial numbers 91000 and up