Why Is My Doorbell Transformer Buzzing? Causes and Solutions

If your doorbell always sounds like it’s humming, it’s likely caused by the transformer. Most doorbells have transformers designed to alter the current from 120V or 220V down to about 20V (depending on your doorbell’s electrical demands). When there’s a noticeably loud hum, something’s wrong with the transformer.

Your doorbell transformer is buzzing because the transformer’s core is degrading, causing loud vibrations. Loud humming can also be caused by the doorbell having loose wires connected to the transformer. If the transformer blows, your doorbell won’t work anymore. A subtle hum or buzz is normal.

Although it might seem like a hum or a buzz coming from your doorbell’s transformer is a huge problem, that’s not always the case. That being said, I suggest digging deeper to find the source of the unwanted sounds coming from the unit.

How Do I Stop My Doorbell Transformer From Humming?

You can stop your doorbell transformer from humming with these instructions:

1. Test the doorbell transformer’s wire terminals to know if they’re getting enough electricity. The transformer should read between 120 volts to 220 volts (or around that range). If it’s lower than that, the transformer isn’t getting enough electricity.
2. Turn off the doorbell’s circuit breaker, then inspect the transformer to find out if the core is damaged. Transformers have cores that vibrate as the electrical current changes. As the core wears down over time, the vibrations get louder. This process makes the doorbell transformer buzz or hum.
3. Use rubbing alcohol to remove debris from the doorbell’s electrical terminals, then do the same to the transformer’s terminals. Home Tips suggests using sandpaper and rubbing alcohol to smooth the terminals, making it easier for the wires to solidify their currents.
4. Clean the doorbell’s button if it sticks when you press it. I’ve removed the debris around a stuck doorbell with a toothpick. Anything thin enough to get around the button will work. A stuck doorbell can cause humming and buzzing sounds, making you think it’s coming from the transformer.

Another way to know if your doorbell’s transformer is failing is if it starts using more electricity. Test the terminals going to the doorbell from the transformer. This common issue also happens when heating pads use more electricity than usual.

Is It Normal for a Doorbell Transformer to Hum?

It’s normal for a doorbell transformer to hum quietly, but you shouldn’t hear it out front of the house. Most doorbell transformers hum because they’re vibrating while reducing the electrical current. These vibrations hum, but they shouldn’t be too noisy.

Many household devices have transformers. For instance, desk fans last longer when they have transformers because they can supply a steady amount of power without surging the circuit breaker. The addition of a transformer can make most appliances hum, including doorbells.

However, there comes a point when your doorbell’s transformer gets too loud.

Here are some of the ways you can know if your doorbell’s transformer makes too much noise for normal operations:

• It’s loud enough to hear from in front of your home
• The transformer buzzes or hums enough to vibrate the walls around it
• You can feel vibrations on the doorbell coming from the transformer
• The doorbell’s transformer is getting increasingly louder
• Your doorbell trips the breaker (this one is incredibly uncommon)

A damaged transformer can affect how much electricity your doorbells and other appliances use. A washer uses less electricity than a dryer unless the transformer is damaged and the current is adjusted. The same can happen to a doorbell transformer when it’s on its way out.

If your doorbell transformer is hot while it buzzes, there could be additional problems.

Review some of the explanations below to find out if your doorbell is blown or in operable condition. You’ll also find helpful replacement suggestions.

How Can You Tell if a Doorbell Transformer Is Blown?

You can tell if a doorbell transformer is blown if the doorbell doesn’t work and the transformer is receiving the proper voltage from the circuit breaker. Another way to know if the doorbell transformer is blown is if it suddenly pops extremely loudly.

GVEC Electrician Service reports transformers of all sizes can spark, burn, and explode. If your doorbell’s transformer is showing any of these symptoms, flip the circuit breaker immediately. Once the breaker is off, follow these steps:

1. Test the doorbell transformer’s terminals with a voltmeter to ensure there’s no voltage going to the unit. Never work on the doorbell until there’s no electricity remaining; otherwise, you could get shocked. The average doorbell has low-voltage wires, so there shouldn’t be more than 24 volts.
2. Remove the screws and wires from the transformer, then look for the serial number, make, and model. Set them aside because you’ll need all of these parts and bits of information to install the next transformer.
3. Get a like-for-like transformer for your doorbell, then connect it to the old wires going to the doorbell and the circuit breaker. You don’t have to change your doorbell but now is the time if you want a different make and model.
4. Attach the mounting screws to the doorbell transformer, ensuring it doesn’t move around from the vibrations. Replace any stripped or worn screws. Consider switching the transformer’s location if you can’t use the same holes to mount it.
5. Turn on the connected circuit breaker and test the doorbell transformer’s terminals to make sure they read between 120V to 220V. The incoming current should be the same as the circuit breaker, whereas the outgoing current should be the amount required by the doorbell (it will be significantly lower).

Once you’re done with this process, check if your doorbell is getting around 20 volts (or however many volts the manufacturer listed on the unit). If your transformer doesn’t reduce the voltage properly, you’ll have to contact an electrician to check the wires.

Note: Electrical appliances always trickle a small amount of power when they’re plugged in, including doorbells. This slight energy flow can make your doorbell start buzzing and humming. You can unplug your space heaters, heating blankets, blenders, and other appliances, but not your doorbell. A little bit of doorbell transformer buzzing is very common and expected.