How to Test the Battery & Voltage Regulator on a Harley Davidson

by Kat Oakley
une harley image by Géraldine Royer from

Some Harley owners like to fix their own bikes, thereby saving both money and riding time. A Harley Davidson can experience electrical problems at any time, but there can be a wait for a service appointment at some repair shops. The most common cause of electrical problems on a Harley Davidson is the battery or the voltage regulator. Troubleshooting can be performed in any garage, and it saves on expensive service bills.

Test the Battery

Step 1

Check the voltage of the battery while it is disconnected from the bike using the multimeter. The volts should be no less than 12 volts.

Step 2

Connect the battery to the bike. Reconnect the multimeter to the battery.

Step 3

Turn the ignition to the "on" position. Do not turn the engine over. The volts will drop slightly, but not below 10 volts.

Step 4

Turn the ignition and start the bike. The volts should not drop below 9.6 volts when the starter engages.

Turn the throttle to rev the engine. As the engine is revved, the volts should go up to 13 or 14 volts.

Test the Regulator

Step 1

Identify the wires. The battery charge lead runs form the voltage regulator to the positive side of the battery. The AC output lead wire leads from the voltage regulator to the stator.

Step 2

Check the ground wire first to ensure that it is properly attached and in good condition. The ground wire leads from the regulator and is bolted to the frame.

Secure or replace as necessary.

Test the Diode Function of the Voltage Regulator

Step 1

Change the setting on the multimeter to Diode. If any of the following tests fail, the voltage regulator needs to be repaired or replaced.

Step 2

Clamp the multimeter positive lead on the AC output wire and the negative lead on the battery charge wire. The multimeter should read .5 volts.

Step 3

Reverse the leads by clamping the negative lead on the AC output and the positive lead on the battery charge wire. The meter should read infinite.

Step 4

Place the positive lead on the ground wire or on the regulator and the negative lead on the AC output. The meter should read .5 volts.

Reverse the leads as in the step before and test again. The meter should now read infinite.


  • Any battery or voltage regulator test should be done on a fully charged, fully functional battery.

Items you will need

  • Multimeter
  • Owner's manual

More Articles