How to replace a doorbell transformer in 5 steps

How to replace a doorbell transformer in 5 steps



Today, doorbells have become commonplace. Be it a guest or a delivery man with your much-awaited Amazon package, a doorbell alerts you when someone is at the door. However, just like other household devices, doorbells can surprise you with sudden breakdowns. Generally, a fault in the doorbell transformer is the most common reason why doorbells stop working.

A doorbell transformer is a metal box with two terminals that connect to doorbell wires. Every home has a standard electrical voltage between 110 to 120 volts, so the role of the transformer is to cut that down to 10 to 24 volts. This ensures that the doorbell works within the correct voltage to function optimally.

In this article, we walk through the steps to test your defective or broken doorbell transformer and lay down simple steps to replace it. 


How to test your doorbell transformer for failure

Before you test a doorbell transformer for failure, you need to locate it. Generally, the first place you can find a doorbell transformer is around a breaker box or an electrical panel. It looks like a metal box attached to a transformer installed into the panel box itself or to the wall nearby. If not, the attic, basement and garage are other places you can locate it.

Once located, be sure it’s the right transformer, as there may be numerous transformers in the house. For example, houses usually have a transformer for the thermostat. In this case, you can locate the transformer between or near the thermostat and the furnace. Doorbell transformers are 24 volts or lower. So, you can verify the rating listed on the exterior of the transformer. If the volts are higher than 24, then it's likely an HVAC transformer. You can also measure the voltage with a voltmeter. 

Another method to verify the transformer type is by looking at the low-voltage wires connected to it. If these wires match the wires inside the doorbell button or the chime unit, then it's the right transformer. To check the wires, remove the covering on the chime unit or the button. Refer to these steps to test the doorbell transformer:

  • Take a multimeter and set it up to test for AC (alternating current) voltage. Make sure the multimeter is set to a minimum of 24 volts. 
  • Now connect the tester probes to the low-voltage screw terminals on the transformer. 
  • A fault in the transformer is proven if the tested voltage differs from the transformer's rated voltage and is more than 2 volts. 
  • However, if the multimeter displays that the voltage is within 2 volts of the rating, there might be a fault in other parts of the doorbell. For example, the circuit, the doorbell button, the chime unit or the low-voltage wiring.


How to replace a doorbell transformer

Replacing a defective transformer is a simple task. Turn off the power, separate it from the wiring and dismantle it. Then take it to a hardware store and buy a replacement. Make sure it has the same voltage rating as the previous transformer. For this process, you will need:

  • Electrical tape
  • Voltage tester
  • Screwdriver
  • Flashlight 
  • Wire stripper
  • Wire caps
  • New transformer

Let’s review the step-by-step process to replace the doorbell transformer.

Step 1. Turn off the circuit breaker for the transformer

Locate the circuit breaker or fuse that powers the transformer. Now either flick the circuit breaker off or take the fuse off the fuse box. 

Step 2. Disconnect the power supply

Turn off the main power to your house so there is no electrical supply. You can do this by locating the main electrical panel and flipping the main circuit breakers at the top so they are turned off.

Make sure you have your flashlight ready so that you can proceed with the repairs. 

Step 3. Disconnect and remove the old transformer

Transformers are usually mounted on the junction box. A junction box contains wires and cables. It is located in the periphery of the house or next to other utility boxes, like the electrical panel or meter box. 

If necessary, remove the junction box cover of the transformer. Keep the screws safe. 

Disconnect the wires that power the transformer. Identify the wires that go from the transformer to the electrical panel and simply untwist them.

Now unscrew the wires that connect the doorbell and the transformer. Release the screws that connect the transformer and the junction box.

Step 4. Wire and install the new transformer

To wire and install the new transformer, follow these steps:

  • Take the new transformer and screw it into the junction box. Start by passing the new transformer’s wires across the hole located on the side of the junction box. 
  • Fasten the screws or bolts (provided with the new transformer) and mount them onto the box. Be sure to keep the electricity off during this process.
  • Connect the existing wires with the transformer’s wires. 
  • Match the transformer's wires to the doorbell’s wires in the junction box. Be sure that the white wires connect to the white wires, and the black wires to the black wires. However, the green wire can be matched with a green or brown wire, or to a metal ground bar or screw. The grounding wire blocks any electrical overload. 
  • Take the endpoints of the matching wires and splice them together with a wire stripper. 
  • Use a wire cap to cover the connection. 
  • Turn the cap in a clockwise direction. For extra safety, cover the wire cap and the protruding wires with electrical tape.
  • Join the low-voltage wire to the screw terminals of the transformer. 
  • Cover the ends of the wires around a terminal and use a screw to hold them in place. 
  • Replicate the process if you need to join another set of wires to the other terminal. 

Step 5. Power the transformer back on

To revive power, turn on the circuit breaker switch or place the fuse back into the fuse box. 

Proceed toward the location of the doorbell button, ring the doorbell, and listen for the chime. If there is a supplementary button, be sure to test that as well. 

Hear a chime? That means your doorbell is functioning properly. If not, try turning off the power again and verify the transformer’s wiring connections are tight. 

If the doorbell still makes no sounds, it’s advisable to seek the help of a professional. 


How much does it cost to replace a doorbell transformer?

If you hire an electrician to repair your transformer, it can cost $260. Whereas, if you go the DIY route, it might cost around $45. A defect in wiring is another common reason why doorbells can stop working. In this case, it’s advisable to hire a vetted electrician. 

If your existing doorbell has worn out and you think it needs replacement, you can purchase a wireless doorbell with a chime that can be plugged into an electrical outlet or run on batteries. 

Today, doorbells come in three types: wired doorbells, wireless doorbells and smart doorbells. Video doorbells, for example, come with a built-in security system and run on Wi-Fi. It’s advisable to invest in a new doorbell if you plan to go on a home improvement spree.


Doorbell repairs are covered under a Cinch warranty

Once you get your doorbell working in tiptop condition or if you plan to purchase a new doorbell system, you want to make sure it works perfectly for years to come. No matter the appliance, sudden breakdowns coupled with heavy repair costs can be bothersome.

Luckily, a home protection plan from Cinch Home Services can help you protect your doorbells (including certain parts and components). If your doorbell stops working from normal wear and tear, simply make a call to Cinch. A vetted and qualified technician will be sent to your home to fix the doorbell. All you need to pay is a one-time service fee. No overbearing repair costs are involved.

Learn more about Cinch, and see if one of our plans is the right fit for your essential home appliances. Get an instant quote today! 


Have a faulty doorbell transformer? Follow these simple steps to replace it.

Your home protection is ready and waiting!