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Motorcycle Voltage Regulator – How to Inspect and Repair the Device

Have you been having challenges working with your motorcycle voltage regulator? Worry no more. This article provides several techniques you should employ when working with motorcycle voltage regulators. Therefore, go through every section of this article to know more about this device.


The working principle of motorcycle voltage regulator


A motorcycle voltage regulator is an electronic circuit that forms and sustains a set voltage output. Besides, this voltage remains constant even when there is a change in the load conditions or input voltage.

Additionally, a voltage regulator maintains the voltage at a compatible range from the power source with the other components. Therefore, since most voltage regulators convert DC/DC, they can also work on AC/DC or AC/AC power conversion. Nevertheless, our primary attention is on DC/DC voltage regulators.


Motorcycle voltage regulator type


Voltage regulators are of two main types. 

  • The voltage regulator for single-phase generator
  • Voltage regulator for three-phase generator


Voltage regulator for single-phase generator


Under this category, there are four types. Therefore, we are going to discuss each one of them.


2-pin Regulator


AC voltage regulator

AC voltage regulator


You will find a 2-pin regulator mostly on small modern bikes that only have the tail lamp and a headlamp. Additionally, these bicycles have no battery. Therefore, since a glowing bulb works best on Ac voltage, there is no need for a rectifier unit in this voltage regulator. Besides, the circuit inside the component controls the AC voltage from the generator to 14-14.5 VAC. Finally, this regulator is an AC voltage controller.


3-pin Regulator


You will find this type of regulator on almost all types of motorcycles. Moreover, in this system, one end of the winding is fixed on the chases of the motorcycle. It goes up to the opposing end of the battery. Additionally, the other end transfers AC voltage to the correction section that changes it to DC. However, it goes through to the regulator section that keeps the voltage output to 14.0V. Therefore, this output voltage charges a 12V or 6V battery hence powering the whole system.


4-pin Regulator (A)


A 4-pin motorcycle voltage regulator is the common type that you will find in most motorcycles. However, the two ends of the stator winding connect to the rectifier section that charges the voltage from alternating current to direct current. Additionally, the regulator maintains the voltage level to 14.0V.


4-pin Regulator (B)


The stator in a 4-pin voltage regulator has two windings. Therefore, one winding carries power to the electrical system and for charging the battery. Besides, the other end supplies power to the tail lamps and headlamps. Therefore, this type of voltage regulator unit combines a 2-pin regulator and a 3-pin regulator. Nevertheless, the 2-pin regulator section offers a 14.0-14.5V alternating current for the lamps, and the 3-pin regulator offers 14.5 direct currents for the battery.


The Voltage regulator for the three-phase generator


Three-phase generator

Three-phase generator




This type of AC voltage regulator works under the same mechanism as in the 3-pin regulator section. However, the difference is only on the layout and components in the device.


Delta type


It is an automatic voltage regulator that is common in most Japanese motorcycles.  Additionally, it has an input of about  130 VAC and an output of 220 VAC.


How to Check a Voltage Regulator on a Motorcycle


A voltage regulator fault may be a result of a dead or weak battery. Therefore, it is essential to test the voltage regulator on your motorcycle. Moreover, below are steps you should follow to achieve this.


Step 1: Acquire a multimeter


Three-phase generator

A voltmeter


You can buy a multimeter from an automotive store or a hardware store. Therefore, this device will read the voltage on your motorcycle battery. Additionally, you will know if your regulator is functioning correctly or not from the readings.


Step 2: Open the hood of your motorcycle


Car hood

Car hood


Jerk the lever inside your motorcycle to push the hood. Moreover, unlock the bar below the hood and use it to pull the hood up. Besides, you should be able to view the engine and the battery of your vehicle.


Step 3: Set your multimeter to voltage


Switch your multimeter to voltage. Therefore, the device screen should appear like ∆V. Besides, if you are not sure of the voltage setting, read the manual that comes with the device.


Step 4: Connect your multimeter to the vehicle’s battery terminals using the clamps. 


Therefore, lift the plastic cap on your battery and connect the red clamp to the +ve terminal of your battery. Additionally, connect the black clamp to the –ve terminal.


Step 5: Note the readings on the multimeter display


Car hood

Voltmeter reading


When your vehicle is off, the reading on your multimeter should be over 12V. Therefore, if readings are below 12V, your battery is faulty, and you should replace it.


Step 6: turn your vehicle on in parking mode


Under this mode, reading should go beyond 14.0 volts. Therefore, if your multimeter reading is about 14.0 volts, this indicates that your alternator is charging the battery as required.


Step 7: Rev the engine


Let someone else rev the engine as you check on the readings on the multimeter. Moreover, with the vehicle still under packing mode, press on the gas slowly until the car attains 2,000 RPMs.


Step 8: Check the output reading on the multimeter


If the reading on your multimeter is above 14.5 volts, it means that you have a faulty or broken voltage regulator. Consequently, if the voltage reading is under 13.6 volts, your battery is weak, and you should replace it as soon as possible.


Symptoms and Solutions of Damaged Motorcycle Voltage Stabilizer


Although a voltage regulator malfunctioning is one of the complications that may develop in the long run, the good news is that it is effortless to recognize. Nevertheless, there are several troubleshooting methods that you can employ to identify such. Therefore, below are some of the symptoms of a damaged motorcycle voltage stabilizer and their remedies.


Symptom 1: High Voltage Output


If the output voltage is about 12.5 volts when the car is idle and goes beyond 16 volts when running, this may result from regulator rectifier failure.




Replace your regulator or take it to your mechanic for repair.


Symptom 2: Instrument Cluster fails


Instrument cluster

Instrument cluster


Like in any electrical device, the instrument cluster needs a set amount of power. Additionally, this voltage will help the regulator display everything you require as you drive. Therefore, a faulty voltage regulator may hinder it from working or behaving erratically. Moreover, you will not tell the amount of fuel you have or the speed you are driving. 




Firstly, check if the speedometer and fuel gauge are working correctly. Therefore, if these components are in a good place, check the connection of your voltage regulator. If everything is okay, then replace the regulator.


Symptom 3: Flickering or dimming lights


Dimming headlights

Dimming headlights


You will realize that your interior lights and headlights are not clear lit as usual. Additionally, your stereo system may also fail due to a faulty voltage regulator.




Check the electrical and wiring unit of your vehicle. Additionally, test your lights using a different regulator. Therefore, if they light correctly, replace the regulator immediately.


Symptom 4: Occasional Dips in Power


A faulty voltage regulator may make some components not function normally. Therefore, if the ignition system, fuel pump, and other elements that need a small amount of power fail, your regulator is faulty.




Check the connection of your regulator to the battery. Additionally, confirm if your battery is in place. If everything is okay, consider replacing the regulator.


Symptom 5: Full light Not Working


Too little or too much voltage significantly affects your headlights. Therefore, high-beam headlights need a small amount of voltage to work. If the full light does not work correctly, it means there is an issue with your voltage regulator.




Check the wiring and if the cause is the regulator, consider fixing a new one.


Symptom 6: Battery is dead


A dead battery

A dead battery


Poor management of voltage due to a faulty regulator rectifier may kill your car battery. However, this may arise due to other causes such as forgetting to turn off your car lights.




Replace your car battery as well as the voltage regulator.


Symptom 7: Corrosion


Corroded car battery terminals

Corroded car battery terminals


Your battery terminals and the top may rust as a result of a faulty voltage regulator.




Clean the battery terminals using vinegar and repair or install an ideal voltage regulator.




A voltage regulator does a lot for your motorcycle, which is why you should regularly maintain it. Therefore, anytime you face a challenge working with your voltage regulator, revisit this article to get the solution. Finally, do not hesitate to share this piece with your social platforms such as Facebook, Pinterest among others.