Detach the button from the wall. If the mounting screws are not visible, you may need to snap off a cover to reach them. To remove a small, round button, pry it out with a screwdriver. Clean away any debris. Make sure wires are not broken. Tighten terminal screws.
If that does not solve the problem, detach the wires from the terminals. Hold each wire by its insulation and touch the bare wires together. If you get a tiny spark and the chime sounds, replace the button. If you get a spark and the chime does not sound, test the chime (Step 4). If there is no spark, check the transformer (Step 5).
If a chime does not sound or has a muffled sound, remove the cover and clean any dust or gunk. Make sure the wires are firmly connected to the terminal screws. If there is corrosion on the connections, detach and clean the wires and terminals with steel wool or fine sandpaper.
Set a multimeter to a low AC reading and touch the probes to “front” and “trans” terminals, then to “rear” and “trans.” If you get a reading that is close to the chime’s voltage rating, power is entering the chime. That indicates the chime mechanism is not functioning and the chime needs replacing.
If there is no power at the chime, test the transformer. Remove the thin wires. Touch the probes of the multimeter to both terminals. If the reading is more than 2 volts below the transformer’s output rating, replace the transformer.
Before you replace a transformer, make sure power is reaching it. If the transformer is attached to a receptacle box, insert the tester probes into the receptacle slots. If the transformer is attached to a junction box, carefully remove the cover and test the wires. Remember, these are 120-volt wires.
If the transformer doesn’t work, buy a new one with the same voltage rating. Shut off power to the circuit. Open the box and disconnect the transformer wires. Remove the nut that clamps the transformer to the box and pull out the transformer. Wire and clamp the new transformer.
If the transformer tests OK but no power reaches the chime or a button, the wiring is damaged. You may be able to attach new wire to the old and pull the new wire through. If you can’t rewire install a wireless chime.
In a single-button chime system, an electrical circuit runs from the transformer to the button, then to the chime and back to the transformer. When the button is depressed, the circuit is completed and the chime sounds.
In a two-button system, a separate wire runs from the chime to the transformer to create a complete circuit for both buttons.