How to Test a Generator With a Multimeter?

Whether you need to improve your camping or tailgating experience or power devices in a remote location, your generator should produce the right voltage. But how can you check if it is producing the right voltage? You can do so by using a multimeter. 

A multimeter is a device that can take multiple readings. You can measure current, voltage, and resistance. Some advanced multimeters can also measure capacitance and frequency. Therefore, people prefer to use multimeters instead of voltmeters to test the generator. 

A digital multimeter is recommended as it provides accurate readings. This article will discuss how you can test a generator with a multimeter. However, make sure that you take all the necessary precautions while handling the generator. 


What Generator Tests Can You Perform Using a Multimeter?

With a multimeter, you can perform the following tests on a generator. 

  • Amperage Tests: Generator amperage tests are of high level. Its circuit is transmitted via a multimeter. 
  • Voltage Tests: You can perform a voltage output test on a generator without breaking the circuit. 
  • Resistance Tests: You need to disconnect the circuit from the coils, generator, and conductors to get correct resistance readings. 

Make sure to keep away from touching the voltage regulator or wires while testing. It can result in electric shock. That’s why it’s better to wear gloves while doing the test.


Testing a 12V Portable Generator With a Multimeter 

Car generators are fitted inside the car to charge the battery and produce power. On the other hand, portable generators are the excellent emergency backup power source for different purposes. 

Before you start the test, you need to carry the following tools with you:

  • A digital multimeter
  • Shoes or sandals having non-conductive soles
  • Protective gloves

Below are the steps to follow to accurately and safely test a generator with a multimeter.

  1. To measure the AC voltage, set the multimeter at V. You can set the voltage between 0-20V range for car generator or 12V portable generator. 
  2. Power on your portable generator and turn on the engine for the generator fitted inside your car. Maintain the speed of the engine at more than 1500 rpm. 
  3. Situate the positive and negative outputs. Your portable generator consists of two wires internally connected with a plastic connector at the end. There, you will find the negative and positive connectors.
  4. Now, connect the red wire to the positive terminal and the black wire to the negative terminal of the generator. 
  5. For your car generator, you will find the two terminals with labels “B” and “Gnd.” Further, connect the black wire from generator to Gnd terminal and red wire to B terminal. 
  6. Now, carefully note down the reading displayed on the multimeter. For a 12V generator, the reading should be between 11-13 volts. However, if the reading displays less than 11V, that means the generator does not have enough voltage. 
  7. Once you have noted down the readings, turn off the car engine and your portable generator.   

Troubleshoot With Multimeter

You can understand and troubleshoot the problem if your generator produces less than 11V using a multimeter. 

  • Disconnect the automatic voltage regulator from the generator. 
  • Disconnect the black and red leads that go from AVR towards the brush set.
  • Cover the leads to avoid connection with the housing.
  • Look for a 12V DC power source like alligator clips.
  • Attach the clips on the brush set of the generator.
  • Keep the positive line attached and power the generator. Next, connect the negative line to the brush set. 
  • Now, put the multimeter leads above the generator leads you detached from the AVR to test. 

Your multimeter should show a minimum of 60 volts. However, if the readings are not accurate, there might be an issue with the automatic voltage regulator. 


Final Thoughts

It is easy to check whether the power output of your portable or car generator is safe with a multimeter. If the voltage meter readings are strange or inaccurate, you can perform the doable troubleshooting process. However, you need to be careful and wear protective gloves while performing the test.

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