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Generator AVR Testing: Easy Step-by-Step Troubleshooting

Generator AVR Testing
Written by Jamie Masterson

An automatic voltage regulator (AVR) is a device that protects generators from electrical surges. When an electrical surge happens, the AVR regulates the voltage coming through it.

You always want your AVR working properly, otherwise, you can experience power failure in your equipment or worse, an electrical fire. AVRs need to be tested constantly, so we’re going to be showing you how to keep your AVR running its best, always.

Signs of a generator AVR Failure

Before you test your AVR, you should check for signs of AVR failure. Here are some signs to look out for.

1. Excessive power surges

If you are experiencing a lot of power surges, chances are they are wreaking havoc on your AVR. When your generator has a power surge, the AVR cannot take a lot of change in power quantity repeatedly.

The AVR also doesn’t work well when there is a lot of unexpected change in power. One of its functions is to regulate current. It takes some time to regulate things. When there are a lot of power surges, the AVR can get damaged.

If you are having a lot of power surges, there could be an electrical issue in your building. Check your electrical wiring to make sure there are no issues. Also, make sure your generator is able to handle the power load you require.

2. Overload

Overload is the most common problem that messes with the AVR. If you are using a generator that can handle less than your power requirement, overload is going to happen.

When your generator is running more power than it can handle, the motor speed will decline. When that happens, your voltage will decline as well. The AVR is meant to keep a certain voltage, so it will overwork itself trying to maintain the set voltage.

Always make sure your voltage usage and the generator’s power capacity match up, otherwise overloads will reduce the life of the unit.

3. Short circuit

A short circuit is a surefire way to kill your generator. It happens when the current quickly strengthens, causing the current to draw too much power from the supply. When this happens, your AVR can overload and short out, making it less functional.

4. Uneven generator speed

A single problem with your generator can cause more problems. A good example of this is when your generator’s motor is moving slowly. A generator has a certain number of revolutions per minute, or RPM, that it is meant to run at.

A problem can cause the motor to run at different RPMs while it’s on. This will affect your AVR by making it work harder for less voltage. Your AVR can short out if it is working too much, so always make sure all of the parts of your generator are working properly.

5. Excessive noise

AVR generators run at relatively low volumes. The average AVR generator will run at around 70 decibels. If your generator is running loud, then there is a chance your AVR is not working properly.

The AVR regulates power, which also works to keep the volume under control. If your generator is running loud, that means that the generator is running too much power. This could be an AVR problem, so always check it when your generator is very loud.

How to Test a Generator Avr With a Multimeter?

If you’re having trouble with your generator, using a multimeter to test the electrical systems on your generator is the best way to pinpoint where the issue is. However, to test if the AVR is the problem, you will need to test a few other parts first.

Before you start, you will need a wrench and a multimeter. Here’s how to test your AVR with a multimeter.

  1. First, you will need to remove the cover of your motor. Do this before you turn your motor on, using the wrench to take off the bolts.
  2. The AVR is the black, plastic box on the bottom left side of the inside of the motor. You will need to remove it.
  3. To remove the AVR, find the two wire attachments on it and follow them to the clips. Open the clips to detach the AVR.
  4. Next, unhook the two tabs at the top. The one on the left is positive, and the right one is negative. Make a note of this.
  5. Once done, use the wrench to unscrew the bolts keeping the AVR in place, then remove the AVR from the motor.

We’re now going to test the electrics.

  1. First, turn on your generator and set your multimeter to volts, or “V~”
  2. Now test the brushes or the two tabs on top. Place the red wire onto “positive” and the black onto “negative.” Your multimeter should be reading around five volts. If you are running over ten volts, there could be a serious issue.
  3. Next you are going to test the windings. These are the red and black wires on the bottom right of the motor.
  4. Each winding is labeled the following from right to left: L1, L2, R1, R2.
  5. Use the multimeter to test three winding combinations: L1 and L2, R1 and R2, and L1 and R1. All readings should read five volts
  6. If all of your readings are the correct voltage, then the problem is with your AVR. If the voltage isn’t correct, then it may be a different problem.

How to troubleshoot an AVR?

You can troubleshoot your AVR using a few different methods. To troubleshoot your generator’s AVR, try the following steps.

  1. You can check the CPU and monitor power. If the CPU isn’t working, the AVR can’t regulate the voltage of the generator. If there is no power on the monitor, then it is a connection problem because your AVR isn’t getting power.
  2. Make sure the other electrical units and the AVR are connected properly. The AVR needs to be connected to everything to get an accurate voltage reading to keep things under control.
  3. The connection between the main power supply and the AVR may be compromised. This means that the AVR doesn’t have any power to regulate voltage or is unpowered and isn’t reading anything.
  4. Try a different outlet to the main power supply. Sometimes the outlet and the AVR don’t sync up properly.

Can you customize a voltage regulator?

There are AVRs with different models that can handle more voltage than the default one. You can find an electrician or a parts supply store that sells AVRs to buy a new one. You can also build one yourself if you are handy with electronics.


Q. Can a generator run without AVR?

A generator can run without an AVR but it’s not recommended. There will be a lot more power fluctuations, which can lead to overloading or surges. Worst of all, the AVR protects the other parts of the motor from blowing. Without it, your generator is at a higher risk of blowing up, which can be deadly.

Q. What is standard AVR?

The standard, predetermined voltage for a generator is between 120 to 240 volts. The AVR will work to maintain that standard.

Q. Where does the AVR get power from?

The AVR gets output voltage from its main coil, then forwards it to its exciter coil. The exciter coil supplies the power to the AVR. The main roll also sends voltage to the AVR that uses it to determine how much voltage is needed.

About the author

Jamie Masterson

With decade-long experience as a generator technician, Jamie has worked with USA’s top generator manufacturers and suppliers as an independent contractor.

The long years of service to the industry has taught Jamie the ins and outs of troubleshooting, repairing, and maintaining all kinds of generators in home, industrial and outdoor settings.

Jamie thinks this platform is a great opportunity to share his tips and tricks with you so you can make the most of such power equipment for better living.

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