We have a doorbell in our home that no longer works. There is appropriate power to both the outside buttons (18v) and the inside chime (16). My husband is an electrician. I am writing this without his terminology but when the buttons are pressed, the center part or plunger doesn't come out far enough to strike the chimes. the plunger does not move freely back and forth when moved by hand. I cannot find the model number on your site, probably because the home was built in 1988 and this doorbell is original to the home. The model number is C8806 and it is a 16 volt unit. The part that we need has no number on it but on the front it has the words " REAR, TRANS, FRONT" on it.