The voltage regulator on a Harley-Davidson motorcycle takes the AC current supplied by the stator/rotor and converts it into 12 volts DC. The regulator is typically located on the front of the motorcycle, mounted to the frame. It is an non-repairable part and it must be replaced when it breaks. Checking its function involves the use of a digital multimeter and a trouble light.
Regulator Bleed Test
1. Unplug the regulator from the engine crankcase.
2. Touch a trouble light to a known ground on the motorcycle and to the pins in the regulator plug, one at a time.
3. The regulator is bad if the trouble light comes on. If not, reconnect the regulator plug to the engine crank case.
Voltage Output Test
4. Place transmission into neutral and start the motorcycle.
5. Place the positive and negative leads of a digital multimeter onto the positive and negative connections of the battery. Set the multimeter to read DC volts.
6. Rev the motorcycle engine to 3300 rpm. The multimeter should read between 14.3-14.7 volts. If it is outside of this range, the regulator is bad and must be replaced.