Doorbell Not Working: Button, Chime or Transformer?

A wired doorbell is a simple low-voltage circuit: a transformer steps household power down to a low voltage, thin wires carry it to the button at the door, and pressing the button completes the circuit to the chime inside. Because there are only three parts, finding the failure is a process of elimination. Most of the work is on the low-voltage side, which is much safer than household wiring, but the transformer connects to a regular circuit on its other side.

Diagnose the symptom

Symptom	Most likely cause
Nothing happens at all	Tripped breaker, failed transformer, broken wire, or failed button
Chime hums but does not ring	Stuck or dirty chime plunger, or low transformer output
Chime rings faintly or only “dings”	Weak transformer, dirty plunger, or loose chime wire
Front door works, back door does not	That button or its wire has failed
Chime rings constantly	Stuck button or a short in the button wiring
Stopped working after installing a video doorbell	Transformer too small for the new device

Step 1: Test the button

1. Unscrew the button from the door frame and pull it out gently.
2. Look for corroded or loose wires at its two terminals. Clean corrosion and tighten the screws.
3. Disconnect the two wires and briefly touch their bare ends together. The voltage on this side is low, but avoid touching the bare ends yourself.
4. If the chime sounds, the button has failed. Replace it.

Step 2: Check the chime

Remove the chime’s cover. You will see small terminals labeled “front”, “rear” and “trans” (transformer), and one or two plungers that strike the tone bars.

• Check that wires are firmly attached to the terminals.
• Make sure the plungers move freely. Dust and grease can make them stick; clean them with a dry cloth. Do not oil them, since oil attracts dust.
• With a multimeter set to AC voltage, measure across the “trans” terminal and the “front” terminal while someone presses the button. If you get a voltage reading but no sound, the chime itself has failed.

Step 3: Test the transformer

The transformer is usually mounted on or near an electrical box in a basement, attic, garage, closet or near the panel. It has two thin wire terminals on its low-voltage side.

1. Set the multimeter to AC volts and touch the probes to the two low-voltage terminals.
2. Compare the reading with the voltage printed on the transformer label. Very low or no voltage means the transformer has failed or has no power.
3. Check the breaker for the circuit that feeds the transformer.

Replacing a transformer means working on its line-voltage side, which connects to household wiring. Turn off the breaker and verify with a non-contact voltage tester before disconnecting anything. If you are not comfortable with that, have an electrician replace it.

Video and smart doorbells

Smart doorbells often need more power than the original transformer supplies and may require a specific voltage and power rating. If an old chime and transformer stop working after a video doorbell is installed, check the doorbell maker’s requirements; an upgraded transformer or a power accessory supplied by the manufacturer is often needed.

Finding a broken wire

If the button tests good, the chime is fine and the transformer has its rated output, the thin wire between them may be broken. Common spots are where the wire passes through the door frame, behind trim that was recently nailed, and in exterior walls where it was stapled too tightly. With the transformer disconnected, a multimeter’s continuity setting can test each run: twist the two wires together at the button, then check for continuity between the matching terminals at the chime. No continuity means a break, and running new low-voltage wire, or switching to a wireless chime kit, is the fix.

Common mistakes

• Replacing the chime first. Buttons fail far more often.
• Assuming the transformer is fine because the breaker is on.
• Oiling chime plungers.
• Ignoring a hot or buzzing transformer. A transformer that is very hot or smells burnt should be disconnected and replaced.

When to call an electrician

Call a licensed electrician if the transformer must be replaced and you are not comfortable working on household wiring, if the breaker feeding it trips when the doorbell is used, or if the transformer is hot, buzzing loudly or discolored. ESFI lists burning smells and buzzing among signs of a possible wiring problem, and recommends a qualified electrician inspect any system that shows them.