How to Test a Motorcycle Rectifier using a digital multimeter

Having a functioning rectifier regulator is one of the key elements to maintaining a healthy and reliable motorcycle. The rectifier regulator converts AC power to DC allowing the alternator to charge the battery, and controls the amount of power delivered to the battery. Without a functioning rectifier-regulator, a weak, dead, or overcharged battery would be the result. In the case you are experiencing these symptoms, a digital multimeter can be used to test the rectifier function. This handheld tester allows you to test the voltage and will help determine if the rectifier should be replaced.


Things to Note

  • The multimeter should be set to Volts DC. 
  • You will be looking for a voltage range of 13.2 Volts DC and 14.8 Volts CD. If you are seeing lower readings, that implies that there is a failure in your charging system and the rec/reg may be the culprit. If it’s higher, operating the motorcycle could be causing damage to your battery as well as any voltage-sensitive electronics on the vehicle. 
  • It is important that you exercise caution when testing the voltage to avoid being shocked and you should know the basic safety requirements for working with electric systems. If you are unsure of your skills, it’s best you take your motorcycle to a qualified technician.


If you believe you are qualified to proceed, then the next step is to check running voltage across the battery.

Steps for Testing Battery Voltage

Step 1

Set your multimeter to measure DC voltage and connect the positive and negative leads to the matching battery terminals. Your battery should be charged, giving you a reading of approximately 12.5-12.9 volts DC (check your particular battery’s specifications for exact numbers).

Step 2

Start the motorcycle and rev the motor to 5000rpm.

Step 3

Using the multimeter, test the same battery terminals again. You should receive a reading of 13.5 to 14.5 volts if your rectifier-regulator is functioning correctly.

If the readings are not within the normal range, it is time to begin testing the charging system components. Ricks Motorsport Electrics offers the industry’s most reliable OEM rectifier-regulators, including a full line uniquely designed to also work with lithium ion batteries. Click here to learn more.