How to Test a Ballast with a Multimeter

An electronic ballast, also called the starter, is a device that limits the current load of devices like tube lights or fluorescent lamps. If you face any problems with it, you can easily test it with a digital or an analog multimeter.

A digital multimeter is more powerful than the analog one and will let you find the measurements of DC and AC voltage, current transmission, and high digital resistance. It is divided into 4 sections: a digital display, controls, dial, and input jacks. It offers significant advantages in precise readings with zero parallax error.

Adjust the settings of your digital multimeter to a thousand ohms resistance. Then connect the black lead to the white ground wire of your ballast. Test every wire with the red lead. If your ballast is good it will return an open-loop or maximum resistance reading.

mechanic with gloves holding a ballast

How Can You Detect a Bad Ballast?

The ballast is necessary to send the proper amount of electricity to electrical devices like fluorescent bulbs. The Ballast is responsible for providing voltage to the bulbs and lowers the current to normal levels when electricity produces a light source. Without an appropriate ballast, the fluorescent bulb can burn out due to a direct 120-volt current. Check the ballast if you hear a buzzing sound from the fixture or bulbs. You can detect this through the following steps. (1, 2)

Testing Process

This method is less time-consuming and provides an accurate ballast test. Here I will mention the steps to test the ballast using a multi-meter.

  1. Turn Off the Circuit Breaker
  2. Remove the Ballast
  3. Set Multimeter Ohm Setting (For beginners, click here to know how to read ohms on a multimeter)
  4. Connect the Multi-meter Probe with Wire
  5. Re-install

1. Turn Off the Circuit Breaker

a pointer finger almost touching the on and off button

Make sure to turn off the circuit breaker before starting any electrical work. Turn off the breaker and switch that are connected to electrical devices, which you are demanding to test.

2. Remove the Ballast

Different machines hold a different range of settings. Ballasts are connected with bulbs, so remove the bulb according to the settings cited by the manufacturer. U-shaped bulbs connect with spring tension, while round-shaped bulbs connect with a socket along with the ballast. You can remove them in a clockwise or counterclockwise direction.

3. Multimeter Ohm Settings

technician testing switches with multimeter

Adjust the settings of your digital multimeter to a thousand ohms resistance. If you’re using Cen-Tech digital multimeter, here’s a guide on how to use it for checking the voltage.

4. Connect the Multimeter Probe with a Wire

You can then insert the new probe of the multimeter into your wire connector. Choose the one that holds the white wires. You can associate the remaining probes with the red, yellow, and red wires that lead from the ballast. The multimeter will return max resistance suggesting zero current travels between ground wore and other ones, and it will sweep to the right face of the multimeter if the ballast is in good condition. However, if it senses current in between, there is no option but to replace it.

5. Re-installation

You can install the new ballast when required. After replacing, install your fluorescent bulbs and replace them with a lens cover. Turn on the power back button at the circuit panel to turn on the fixture.

(1) electricity –
(2) burn out –

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About Sam Orlovsky

b1d87d2ee85af3e51479df87928bdc88?s=90&d=mm&r=gCertifications: B.E.E.
Education: University Of Denver - Electric Engineering
Lives In: Denver Colorado

Electrical engineering is my passion, and I’ve been in the industry for over 20 years. This gives me a unique ability to give you expert home improvement and DIY recommendations. I’m not only an electrician, but I also like machinery and anything to do with carpentry. One of my career paths started as a general handyman, so I also have a lot of experience with home improvement I love to share.

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