Repair a doorbell that stopped working

Doorbells operate on a simple low-voltage circuit that fails in predictable ways. A transformer steps household current down to 16 or 24 volts, runs through a button switch, and triggers an electromagnetic chime. The system works flawlessly for years until corrosion creeps into the button, a wire shakes loose during a paint job, or the transformer quietly burns out in the basement. The repair takes an hour and requires no special skills beyond methodical testing. Most fixes cost under ten dollars. You will need a multimeter to check voltage at three points in the circuit. Once you identify which component has failed, replacement is straightforward. The satisfaction of hearing that chime again after months of knocking is disproportionate to the simplicity of the fix.

1. Touch wires, verify source. Remove the doorbell button from its mounting by unscrewing or prying gently with a flathead screwdriver. You will see two wire terminals on the back. Touch the bare wire ends together. If the chime sounds, the button has failed and needs replacement. If nothing happens, the problem lies deeper in the circuit.
2. Find the transformer. The transformer is usually mounted near your electrical panel in the basement, garage, or utility closet. It is a small metal box with two thin wires leading to the doorbell circuit. Check that these wires are firmly attached to the screw terminals. Look for scorch marks or a burnt smell indicating transformer failure.
3. Measure transformer voltage. Set your multimeter to AC voltage. Touch the probes to the two low-voltage screw terminals on the transformer. You should read between 16 and 24 volts depending on your system. No reading means the transformer is dead. Verify the transformer is receiving power by checking for 120 volts on the input wires, then replace it if the output is zero.
4. Check chime box terminals. Remove the cover from your chime box, usually mounted on a hallway wall. Check that all wire connections are tight on their terminals. Look for wires labeled front, rear, and trans. Wiggle each wire gently. If one pulls free easily, strip a fresh half-inch of insulation and reconnect it securely under the terminal screw.
5. Swap the transformer. Turn off the circuit breaker feeding the transformer. Disconnect the 120-volt wires using wire nuts and remove the mounting screws. Install the new transformer in the same location, connecting black to black and white to white with wire nuts. Attach the low-voltage doorbell wires to the output terminals. Restore power and test.
6. Install new button. Unscrew the old button and disconnect the two wires. Connect the wires to the new button terminals in any order since polarity does not matter in this circuit. Mount the button with the provided screws. Test immediately before sealing any caulk around the edges.
7. Clear corrosion away. If components test functional but the chime is weak or intermittent, corrosion is limiting current flow. Spray electrical contact cleaner on all terminals inside the button, chime box, and transformer connections. Scrub gently with a small wire brush or folded piece of fine sandpaper. Wipe clean and reconnect.
8. Ring it all. Press the doorbell button and listen for a full, clear chime. If you have a rear door button, test it separately. The chime should produce distinct sounds for front and rear signals. If the chime is weak, check that wire connections are tight and consider replacing an aging chime mechanism.