If your door chime no longer provides the familiar tones and merely buzzes, you can probably fix it without too much trouble. Try this before replacing it.
Step 1
Remove the cover of the chime unit. Many times this cover will just hang on some tabs and can be removed by lifting it straight up. Other types may require that screws be loosened or removed.
Step 2
Look for obviously broken or missing parts. Reinstall if possible. Springs and plungers are basically the only moving parts for electro-mechanical chime units.
Step 3
Tighten electrical terminal screws. Most units operate at 24 volts or less, and should not pose a shock hazard. You can determine this by looking at the wires. If the wires look to be closer in size to telephone wire - or low voltage thermostat wire, it is most likely the 24 volt (or less) type. Low voltage door bell circuits usually originate at a small 120 volt to 24 volt (may be any value between 12 and 24 volts) transformer connected to the side of electrical panel. The presence of a transformer is also a good indication, too. In any case, treating the wiring as if it was line voltage (120 volts) will help prevent getting hurt.
Step 4
Listen carefully and then observe the moving parts while an assistant presses the door bell button several times. A faint buzzing sound or slight movement confirms that the chime unit is getting powered.
Step 5
Check and tighten the electrical points (fuses and circuit breakers, terminal screws of the door bell button(s), and transformer) if unable to hear or see the indications above and try again. If still unable to hear or see the indications above, just continue following the steps below.
Step 6
Check the plunger for freedom of movement. Gently push / pull the plunger(s). It may move only in one direction, but may move in both. If unable to move the plunger, or it moves but does not "spring back" into position, it is likely hanging up on dirt, dust, etc.
Step 7
Clean the moving parts of the chime unit. This can be done in place or removed from the wall. Either way will require safeguarding the area from dirt, solvents, etc. If removing from wall, label the wires and terminals before disconnecting. Spray a short blast of electrical contact cleaner at the moving parts. Do not be surprised to see black contact cleaner dripping out of the mechanism. Attempt to move the plunger again. Continue to spray bursts while moving the plunger. The idea is to flush out any dirt, etc that has collected around the metal plunger body. Once there plunger is able to move freely, the chime unit is ready to be (reconnected and) tested by pressing the door bell button.
Step 8
Compare the voltage rating of the chime (likely 12 to 24 volts) with the rated output stamped on the transformer. These values must match. Replace either the chime or transformer so that the two have matching voltage values. Most doorbell transformers have a 25 VA rating (VA is "Volt Amps" - do not confuse with Volts).
Step 9
Remove wires from door bell buttons and touch wires together. If chime works, replace door bell buttons.
Warnings
- Do NOT lubricate the plunger. Lubricants attract and hold dust and dirt. This will cause the plunger to fail prematurely.
Things You'll Need
- Screw drivers
- Electrical Contact Cleaner (aerosol) from home center / hardware store.
