Rear doorbell not working

doorbell

A neighbor ask me to help him figure out why his back doorbell isn't working. When I arrived, the back door button was gone. I know you should just be able to touch the wires together to get the chime to go off. The back doorbell wires go straight to the chime. The front doorbell wires go to the transformer. There is another set of wires at the transformer that go to the chime. The two reds are on the transformer and the whites are wire nutted together. The front doorbell works fine. I can't get my mind wrapped around this wiring setup. My question is, will this set up work with the back doorbell wires going straight to the chime? I have tested the wires with an ohm meter so I know the wires go to the back door and they are not broke anywhere. Any ideas how I can wire this up without the wires from the back door going to the transformer? Thanks for any help.

Best Answer

The transformer-button red wire is supply hot or "R" in thermostat speak.
The white wire is "front button switched-hot".
The chime-transformer red wire is return/common/neutral or "C" in thermostat speak.

You need to bring supply hot, and "rear button switched-hot" to the other doorbell.

... presuming the doorbell has 2 different chimes.