Project Guide
How to Find and Test a Doorbell Transformer
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Time Required: Under 2 hours
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Difficulty: Intermediate
A transformer keeps wired doorbells powered at the right voltage for optimal operation. It looks like a small metal box and can be silver, off-white or even brass colored. If your doorbell is no longer working, you may need to troubleshoot the transformer in order to perform the repair. This guide will explain how to find and test a doorbell transformer.
Doorbell Transformer Location
- Doorbell transformers are usually located outside the home along the siding or on a wall in the garage.
- They may also be fixed to a wall in the basement or closet near the front door or entryway.
- If you don’t see it in any of these places, check the walls in the attic. It may be tucked behind the insulation.
- For homes with visible doorbell wires, you may be able to trace them back to the location of the transformer.
Check the Doorbell Transformer Wiring
- Before you run any voltage tests, check the doorbell transformer wiring and make sure it’s properly connected.
- Cut the power by switching off the main breaker in your home.
- Doorbell wire is usually 18-gauge and should be free of splices, tears and corrosion.
- If the wire in your transformer appears worn or damaged, you’ll need to replace it.
Doorbell Transformer Voltage
- Test the doorbell transformer voltage by setting the meter on your voltage tester to 25VAC (volts alternating current).
- Measure the voltage on the transformer to see if it’s producing enough electricity. The voltage should be at or around 16.
- If the voltage is too low, replace the transformer to repair your doorbell unit.
