How Do I Know if my Doorbell Transformer is Bad? – Complete Guide!

Asking “how do I know if my doorbell transformer is bad”? Keep reading!

If you’re here because your doorbell is not working or you just want to check your transformer voltage, then this would be the most important read today.

Here we’ll describe the early signs of a bad transformer and how to perform the voltage measurement.

Let’s learn more!

To find out whether a doorbell transformer is bad you’ll need a multimeter to measure the chime’s current and the transformer’s voltage. When your transformer is not working you’ll see an empty reading, otherwise, you would see the current voltage.

About The Doorbell Transformer!

When your Doorbell won’t work, the possible reasons could be the push button, the chime installation, the wiring system, or the transformer.

The primary role of your doorbell transformer is to lower the current from the household’s 120V to 16-24V for the doorbell device.

• The transformer might not be the problem with your doorbell.

When the transformer goes faulty, it will either lower the current down to less than 16V in which case your doorbell won’t be working, or stop the operation.

However, performing a good inspection of your doorbell components and chime’s wiring is a must-do, before a conclusion.

Let’s next attempt to recognize a bad transformer by early signs:

Early Signs of A Bad Doorbell Transformer

It’s hard to tell whether a transformer is bad without measuring the voltage with a multimeter.

However, you might start noticing weird behavior from your doorbell whenever your transformer is bad, months before completely giving up.

Doorbell Restarting:

When your doorbell is frequently restarting the problem could be one of two things.

It’s either a wiring problem related to the chime or your transformer is failing to deliver enough current.

Doorbell Won’t Turn ON:

In case you’ve encountered a problem with your doorbell after restarting the device or after a power outage, then your transformer might be faulty.

However, additional inspection of the other components involved is important before assuming anything.

Humming Sound

If you’re hearing a constant “humming” sound from your transformer’s box, then it’s not too late to save the machine. You’ll need to have an electrician over to repair the device.

No Sound

When you hear absolutely nothing when you’re close to the transformer that wouldn’t be good news for your doorbell.

It’s either your transformer is completely dead or the wiring in between is interrupted so you would need to inspect the installation.

Note: Be cautious when interacting with “humming” transformers.

Let’s now learn how to know when a doorbell transformer is bad…

How Do I Know if my Doorbell Transformer is Bad?

When you’re wondering whether the transformer is good or bad, that often means that your video Doorbell is not working.

In case you just want to check the voltage of your Doorbell transformer the methods below are also going to help.

You’re going to need a multimeter to get accurate readings!

Method #1 Test The Chime

To begin testing the Doorbell transformer you’ll need to open the chime’s cover and inspect the wiring before measuring the voltage.

When your transformer is bad or entirely non-functional when you touch the probes to the wires, the multimeter won’t show a flowing current.

Here’s how to check whether electricity is reaching your doorbell chime:

1. Disconnect the doorbell.
2. Adjust your multiviewer to AC (the letter “V” with a wavy line).
3. Touch the multiviewer probes to the two wires of your Doorbell.
4. Check if there is a voltage.

When you see voltage after your readings, that would be good news! Your transformer is working and is properly connected to the Doorbell’s chime.

The next step would be to measure the transformer’s voltage so let’s learn how in the next method.

Tip: Keep the doorbell disconnected while performing the multiviewer measurements.

Method #2 Check The Transformer’s Voltage

Most Doorbell transformers are located next to the main electrical panel of the household so users shouldn’t have a hard time locating the box.

They are wide and long, most often 2 inches long where two wires are attached with screws.

Here’s how to check the voltage of your Doorbell transformer:

1. Set the multimeter to 25 AC (Altering Current).
2. Locate the wires leading away from your transformer.
3. Do not touch the infeed wires since they carry 120-volt current.
4. Touch the probes of your multimeter to the two wires.
5. Check the readings on your multimeter.

You should see 16 – 17 volts which indicates that your transformer is working well.

Less than 16 volts would mean that your transformer is worn out and needs a replacement.

Note: You won’t need to flip the circuit breaker to perform this measurement.

Method #3 Use A Test Light

In case you don’t have a multimeter you can still test whether your transformer is working normally by using a low-voltage test light.

You won’t be able to acquire accurate readings but the light will tell you whether or not your transformer is working.

You’ll only need a low-voltage test light with at least 10cm long wires from each pole. You’ll need to connect the light’s wires to each screw head of the transformer.

In case the lamp fails to light, your transformer is bad and not working!

Make sure that you’re making a good connection between the screw heads and the lamp’s wires so you won’t receive false output and wrong conclusions.

Note: Make sure to check if the light bulb is working before your test.

How Long Does A Doorbell Transformer Last?

The doorbell transformers are made to last as long as the doorbell device. They are typically long-lasting units covering from 10 to 15 years.

In case this is the time frame in which you’re experiencing the issues, it’s highly likely that your transformer is bad.

How Much Transformers Cost?

In case your transformer is faulty and you would need a replacement of the entire unit, you’ll be looking at $100 – $350, depending on the quality.

Keep in mind that an entire replacement might not always be required, especially when your transformer is still working, good or bad.

How Much Do Electricians Charge?

The better alternative is to hire an electrician to inspect the entire doorbell installation.

Since the professional can inspect the situation, inform you about the problem, and let you know how much it would cost.

The electrician would know whether you need a brand new transformer for your doorbell or a simple repair that will get the job done.

Quick Recap:

Hence, you can tell when a doorbell transformer is bad by measuring the output voltage with a multimeter set to Altering Current. You can also use a low-voltage bulb to test whether it will light upon touching the screws’ head of the transformer.

Read Next: How to Install Ring Doorbell with Existing Doorbell?

Last Thoughts:

Now that we’ve answered the question “how do I know if my doorbell transformer is bad?”, you can perform your measuring and determine the state.

Transformers should deliver 16V to 24V which is necessary for the doorbell and less than that means a replacement.

We hope that this post was helpful and to discover more guides such as this one, make sure to check our online blog.