Door Bell Wiring Troubleshooting Tips
Residential door bell systems are low voltage except the line side of the
transformer. They can range from 16-24 volts. The system is comprised of a
transformer to step the voltage down from 120V to 16, 18 or 24 volts. One or
two buttons for front and back door and a chime unit. Below is a standard
doorbell system wiring diagram.
Doorbell wiring diagram
Color of wires here can be different than what you see and is not important other than
to follow the wires. They are typically 18 gauge wires. First thing to check here is the
transformer. A voltage tester should indicate 16, 18 or 24 volts at the two terminals on
the transformer. If you have voltage there the next place to check is at the chime.
Have someone go to the front door and hold the button in while you check for voltage
between the Common terminal and the Front screw. The same can be done with the
Rear button and the Rear screw. If you get the proper voltage, 16, 18 or 24 volts then
the chime is bad. If you get no voltage when either the front or rear button is pressed
then you need to check the buttons.

The buttons can be checked by removing them and just putting the two wires
together. If you do this and get voltage at the chime unit you know you have a bad
button and it should be replaced.
If you do all this and still get no answer you may need to trace the wire and find a
break or open splice. A typical place to find a splice is behind the chime on the wall.
Most times the transformer or chime fails which is why you will want to check those
first.
(C)Copyright 2003 Forte Electric Inc.
Electrician Tech Pages
Door Bell Wiring Diagrams
& Troubleshooting Tips