How to Check a Harley Voltage Regulator

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.

Difficulty:

Moderately Easy

Instructions

Things You'll Need

• Trouble light
• Digital multimeter

1. 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

   • 1

     Place transmission into neutral and start the motorcycle.

   • 2

     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.

   • 3

     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.

Tips & Warnings

• Consider testing the stator/rotor and the battery at the same time as you are testing the voltage regulator.

• Always use caution when working around electricity. Remove watches and rings to help avoid electrical shock.