My doorbell died on a Tuesday. The delivery guy knocked instead and I missed three packages because I was in the basement with headphones on. When I finally investigated, I assumed the whole thing needed replacing. Turned out to be a $4 part and 20 minutes of work.

Doorbells are simple circuits: a button, a transformer, a chime, and wires connecting them. When it stops working, you check those four things in that order. Most problems are the button or the transformer — both easy fixes.

Start With the Button

The button is outside, exposed to rain and sun. It corrodes. Remove the two screws holding it to the doorframe and pull it away from the wall. You will see two wires attached to terminals. Touch the two bare wires together — if the doorbell rings, the button is the problem. Replace it ($4 at any hardware store).

If touching the wires does nothing, the problem is deeper. Unscrew the wires from the old button anyway, clean the exposed copper with sandpaper until it shines, and attach the new button. Sometimes the wire ends are corroded and not making contact.

Check the Transformer

The transformer is a small metal box — usually in the garage, basement, closet, or attached to the electrical panel. It steps down 120V house power to 16-24V for the doorbell. Use a multimeter set to AC voltage and touch the probes to the two screw terminals. You should see 16-24 volts.

Zero volts? The transformer is dead. Turn off the breaker, note which wires go where (take a photo with your phone), unscrew the old transformer, and wire in the new one ($15-20). If you are not comfortable working inside an electrical box, an electrician will do it in under an hour.

Last Stop: The Chime

Remove the chime cover and look for loose wires. Sometimes a wire slips off its terminal from years of vibration. Tighten the screws with a small flathead screwdriver. If the chime itself is physically broken — cracked plastic, stuck plungers — you need a new chime unit ($15-30).

My doorbell was dead because the button had corroded internally. Four dollars and two screws later, it worked like new. Now I hear every package.