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How to Check a Doorbell Transformer

Checking a doorbell transformer is the easy part; sometimes just locating it can be the real challenge.

A conventional doorbell has wires that connect the chimes or bell to the power source and that run to the button, which acts as a switch.

A conventional doorbell has wires that connect the chimes or bell to the transformer, which reduces standard voltage to low voltage.

Sometimes finding a doorbell transformer is a challenge. It may be located inside the chimes or bell enclosure but often is located elsewhere.

If you know where the doorbell wires run, trace them back to find the transformer’s location. Newer homes often have doorbell transformers conveniently located in plain sight, high on a garage wall.

Sometimes it’s mounted on a floor joist in the basement, below the doorbell, in a closet, in the attic (possibly buried under insulation), or in a crawlspace. Or, it may be located inside an electrical box, near the electrical panel or the doorbell.

The proper voltage rating should be stamped on the transformer and/or the doorbell mechanism.

To check the doorbell transformer:

1Adjust a volt-ohm meter’s scale to 25 VAC. Attach the two probes to the two flat screws that connect the small-gauge doorbell wires to the transformer.

2Compare the reading to the device’s voltage requirements. If it’s too low or exceeds 16 volts, shut off the power to the transformer before doing any more work on the doorbell system. Replace the transformer with a new one, readily available at home centers.

Join the Conversation

  • map0814

    Can I replace my doorbell transformer with one with higher voltage? We need a doorbell that is LOUDER and the doorbell in this old house is very quiet, only one note (ding) and has a 10v transformer. Many of the louder chimes that I find use transformers with higher voltage, can I swap out the transformers?

  • Ray Stark

    Some doorbells don’t have transformers. I found this out the hard way, searching all over for mine only to find out from a licensed electrician that it had no transformer.

    • Joephus

      But wouldn’t that mean your doorbell is running on high voltage? I’m also trying to locate my transformer but I can’t seem to find it! I’m pretty sure mine is low voltage because I tried replacing the front doorbell switch and went into contact with the wire, I’m still alive lol.

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