6 Symptoms of Bad Regulator Rectifier On a Motorcycle

Compare Motorcycle Insurance!
Motorcycle Insurance - Compare and Save up to 40%
It's fast and easy to compare motorcycle insurance quotes! Get My Quotes! Motorcycle Image

Today, I’m sharing an incident that happened a few months back. This could also happen to you. So, read this guide to know how to prepare for the worst conditions.

I was cruising on my Royal Enfield Classic 350, experiencing a fresh wind flow on my face and freedom at my fingertips.

Suddenly, my motorcycle started misfiring, and my headlight started flickering. Initially, I couldn’t figure out what was happening.

I parked it aside and inspected the spark plug to see if there were any carbon deposits on the tip. The spark plug was clean and functioning properly.

Fortunately, I kept an ECU scan tool in the toolbox. So, I inserted the scan tool into the port and connected it to my iPhone via Bluetooth. (Click here to buy one from Amazon.)

I launched the app, ran the ECU scan, and got the P0562 diagnostic trouble code in the scan result.

I quickly understood my motorcycle regulator rectifier had gone bad. (P0562 is the trouble code for “System Voltage Low,” and the RR Unit recharges the battery)

It was easy for me because I have an engineering background and years of motorcycle experience. But it won’t be that easy if it happens to a normal rider.

So, I have listed six common symptoms of a bad regulator rectifier on a motorcycle. This guide will help in diagnosing bad rectifier problems on your motorcycle.

Motorcycle RR Unit

6 Symptoms of Bad Regulator Rectifier On a Motorcycle?

The function of a regulator rectifier on a motorcycle is to regulate and rectify the voltage. The stator generates AC, but the battery needs DC power to store it in chemical form.

So, the regulator rectifier (RR Unit) converts the AC into DC and recharges the battery. If it fails, your motorcycle battery will face charging problems.

Moreover, you’ll also face several more issues if the regulator rectifier goes bad. Here are six common symptoms of a failing RR unit on a motorcycle.

1. Engine Starting Problem

One of the most common symptoms of a bad regulator rectifier is difficulty starting the engine. You may experience a sluggish or delayed start, or the engine may fail to start altogether.

This happens because the regulator rectifier supplies the necessary electrical power to the ignition coil, which starts the engine.

So, if your motorcycle engine is struggling to start, test your regulator rectifier unit and replace it for uninterrupted long rides.

2. Battery Stops Charging

As I mentioned earlier, the motorcycle stator generates AC while the battery needs DC to store in chemical form.

The rectifier circuit converts the AC into DC while the regulator circuit regulates the voltage and maintains between 13.6 and 14.8V.

If your regulator rectifier goes bad, your motorcycle battery will not charge. Also, a faulty RR unit overcharges the battery.

3. Dimmed or Flickering Headlight

If your motorcycle headlight turns on when the engine is running, it means it’s bypassed from the battery and directly connected to the stator power supply.

That’s why your headlight goes off when you turn off the engine. But it doesn’t mean your headlight is directly connected to AC power.

Rather, it’s connected to a regulator rectifier, which supplies DC power when the light glows when the engine starts.

So, a bad regulator rectifier will also affect the functioning of the headlight. A dimmed or flickering headlight is an indication of a malfunctioning regulator rectifier.

This occurs due to irregular voltage regulation, causing fluctuations in the power supply to the headlight.

Note: Ignoring this symptom compromises your visibility on the road and poses a safety risk to you and other motorists.

4. Fluctuating Meter Readings

Irregular speedometer or tachometer needle jumps, fuel gauge irregularities, inaccurate temperature readings, etc., indicate a bad regulator rectifier on your motorcycle.

If you notice a fluctuation in meter readings, inspect the regulator rectifier unit and replace it if it malfunctions.

You can disconnect your motorcycle’s battery negative terminal connection and check the voltage output with a multimeter.

If the output voltage reading is less than 13.6V when the engine is running or the reading fluctuates without twisting the throttle bar, it clearly indicates a faulty regulator rectifier.

5. Battery Draining While Riding

One alarming symptom of a bad regulator rectifier is experiencing a battery drain while riding your motorcycle.

Typically, the regulator rectifier ensures the battery receives a consistent and appropriate amount of electrical power from the charging system.

However, when the regulator rectifier malfunctions, it may allow excessive or irregular power flow, leading to the battery draining while you ride.

6. Engine Misfiring

A bad regulator rectifier could cause your motorcycle engine to misfire. It happens because the ignition system takes electrical power from the regulator rectifier unit.

If the RR unit fails to supply current, the spark plug will face difficulty igniting the air-fuel mixture in the combustion chamber.

I faced engine misfiring when my motorcycle regulator rectifier was faulty. When I replaced the rectifier, the engine misfire issue was resolved.

So, these are some common symptoms of a faulty regulator rectifier on a motorcycle. If you notice the above symptoms while riding, inspect the RR unit and replace it if it’s faulty.

What Happens a Rectifier Fails in Motorcycle?

The function of the rectifier circuit in a motorcycle is to convert AC to DC. If the rectifier fails, your battery stops charging and drains while riding.

Also, You’ll note signs right away like poor starts, fluctuating meter readings, engine misfiring, and dimmed headlights.

Can a Motorcycle Run Without a Rectifier?

If your battery is fully charged, your motorcycle will run a few miles with a faulty rectifier. However, your motorcycle will not run without a regulator rectifier because it regulates the voltage fluctuations and supplies current to the ignition system.

Will Your Motorcycle Start With a Bad Regulator Rectifier?

If the battery is fully charged, your motorcycle will start for some time with a bad regulator, but it won’t run long.

It happens because the regulator rectifier takes AC from the stator and converts it into DC to charge the battery.

Your battery supplies initial power for cracking the engine. Moreover, once the engine starts, the stator fulfills all electricity requirements to run the engine and other electrical components.

So, you must immediately replace the bad regulator rectifier for uninterrupted motorcycle rides.

What To Do If a Motorcycle Regulator Rectifier Fails?

If you’re on a motorcycle ride and its regulator rectifier fails, first switch off the electrical accessories and remove the headlight fuse if there is adequate visibility.

Now, kickstart or bump start the motorcycle and take it to the nearest mechanic garage. If the battery is fully charged, you can easily ride it several miles.

After reaching the mechanic shop, replace the regulator rectifier.

How Much Does a Motorcycle Regulator Rectifier Cost?

A motorcycle regulator rectifier will cost anywhere between $50 to $80. The exact cost depends upon the motorcycle’s make and model.

Above that, you’ll be charged the taxes and mechanic fee for replacement. So, the overall replacement cost will go between $80 to $100.

You can save additional charges by replacing it yourself. However, that requires basic knowledge and extra effort.


The regulator-rectifier (RR Unit) is essential to any motorcycle or car. It converts AC into DC and regulates voltage supply to electrical components.

When the regulator rectifier is faulty, You’ll have difficulty starting, battery charging, headlight flickering, and engine misfiring.

You must have to replace the regulator rectifier if the old one is malfunctioning. It will cost you anywhere between $50 to $80.

I hope you found this article helpful. Do share with your rider friends.

Similar Posts

Leave a Reply

Your email address will not be published. Required fields are marked *