How to Test a Doorbell Transformer Voltage with a Multimeter

For you to ask how to test a doorbell transformer, it could either mean your video doorbell is not working, or you want to know the voltage of your transformer.

Whichever one it is, I will show you how to check a doorbell transformer voltage using a multimeter.

For those that are still looking for their transformer location, see how to find a doorbell transformer.

The primary role of a doorbell transformer is to step down a household current of 120 V to about 16v-24 volts it requires.

When the doorbell system stops working, many things could be responsible. It may be the push button at the front door, the wiring system, the bell chime, or the transformer. So, make sure you find out the cause before assuming that your transformer has gone bad.

Signs of a bad transformer

You can hardly tell if a transformer is bad unless you test it with a multimeter. A reading of 16 to 24 volts shows the transformer is working fine.

If the voltage is Less than 16, call an electrician to replace the transformer because it has gone bad.

How to test a doorbell transformer with a multimeter

Testing a transformer is easy, anybody can do it. All it requires is a functional multimeter and a doorbell transformer.

Switch ON your multimeter

Turn on your multimeter and set the knob to a low voltage setting, often 25 AC volts.

Place each probe on one of the screw terminals of the transformer

A multimeter comes with two wires (probes) that enable you to measure the voltage on any device.

Place one probe on each screw terminal of the transformer.

Read the voltage level on your multimeter.

Once you place the probes on the terminals of the transformer, it will display the voltage reading.

If it is between 16-24V AC, the transformer is ok, but if the voltage is less than 16, change the transformer, it has gone bad

You can buy a new transformer here on Amazon

Can I check the voltage level of my doorbell transformer without a multimeter?

Yes, you can do that by looking at the body of your transformer. You will see their voltage rating. However, it can only be useful for new transformers, as you cannot use the method to troubleshoot an existing transformer.

My doorbell stopped working. What could be the cause?

Many things could be responsible. It may be your doorbell chime, your push button, or your doorbell transformer. Troubleshooting with the system will surely find out the cause.

While troubleshooting starts with the push button because they are the part that spoils often in a doorbell.

Lose out the push button on the door and bring out the wires from the button. Join the two wires.

If the bell rings, you know you have found the fault. If not, check the chime.

Lose the chime’s cover, set the knob of your multimeter to be on voltage, and touch the probes on the wires. Ask someone to press the button for you. If the meter shows that the current is flowing but the bell is not ringing, replace it.

If the chime is good, test the transformer and replace the faulty one.

Test the doorbell wires as well. You can test it for continuity using a multimeter. Make sure it is rust-free.

Is a doorbell transformer AC or DC?

All transformers use AC current, which is in line with Faraday’s law of electromagnetic induction. Doorbell transformers are no exception to the rule.

Also, your home uses alternating currents.

Converting it to DC will require an additional rectifier that may be more complex and expensive.

Is humming doorbell transformers dangerous?

A humming or buzzing sign from the doorbell shows the button may be stuck in the contact position. Early detection and repair will save the transformer from burning.

How can you tell if a transformer is bad?

You can do that by using a multimeter to test the voltage of the transformer. A good transformer usually has a voltage of 16 to 24V. While bad transformers have low or zero power.

You can check the voltage with one of the electrical testing equipment like a voltmeter


You’ve seen it all, including how to test a doorbell transformer and ways to troubleshoot faulty doorbells. apply each technique as we used it in the article.

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About mariaelectricals

Hi, I am Emmanuel Nwankwo, a commercial electrician and the founder of I established this blog to share my decades of work experience in electrical installations and repairs.