If the voltage is too low replace the transformer to repair your doorbell unit.
Door chime transformer replacement.
If the doorbell rings the switch needs to be replaced.
Wiring a doorbell transformer is more complex than replacing a doorbell button or chime unit.
Test the doorbell transformer voltage by setting the meter on your voltage tester to 25vac volts alternating current.
Make sure you understand how to shut off power to the circuit controlling the tansformer before attempting this repair.
The voltage should be at or around 16.
This section will cover how to replace a transformer.
If you need to know how to install a transformer for the first time call a qualified electrician.
Measure the voltage on the transformer to see if it s producing enough electricity.
If the switch isn t the issue head to the chime or the indoor doorbell mechanism.
It will likely be in the immediate vicinity though in the attic right above in the basement or in a nearby closet.
How to replace a doorbell transformer although the doorbell itself operates at low volatagge that is unlikely to shock you replacing a transformer involves working with line voltage circuit wires.
A look around the doorbell should give a pretty good idea where it might be.