When working on doorbells, the heart of the installation is the transformer. A transformer is a device that converts your supply 120 volts to 16-24 volts. The lower voltage will depend on what voltage your doorbell operates on. Most doorbells operate on 16 volts, but always check your doorbells manufacturers specifications for proper transformer sizing. You will need a digital tester that will check voltages from 0-120 volts A/C, it should also check continuity. These testers are relatively inexpensive and available in any building supply store.
The first thing you should check is your panel for a tripped circuit breaker, and with any luck your transformer might be there. If you are not sure how to do this, I have another article on how to complete this task. Once you have verified there are no tripped breakers you can proceed.The hardest, most involved part of troubleshooting a doorbell problem is locating the transformer. They are typically located at the panel, but I have found them in garages, furnace rooms, attics, basements, and closets. Wherever you have 120 volts you can have a transformer. The good thing is they are typically mounted externally, so they are easy to spot. The transformer is somewhat square, about 3" x 3", and the low voltage terminals are visible with a low voltage cable attached. When you have located the transformer test the voltage, you should measure some voltage between 16-32 volts depending on your doorbell. If no voltage is present you will need to verify that there is 120 volts supplying the transformer. This could be difficult or unsafe for most people and might be the end of your troubleshooting. It is probably best to stop at this point and contact a qualified electrician to check, and possibly replace your transformer. If you have voltage at the transformer, you can move on to the doorbell itself.
At this point you will require some assistance. Remove the cover on your doorbell and inspect the wiring inside. You should see 1 set of wires if there is 1 button, and 2 sets of wires if there are 2 buttons. They should be identified by front and back door. unhook only 1 set of wires and attach your meter to them. The meter should be set to AC, and the lowest setting. Check your meter instructions if you are not sure. Have your assistant press the corresponding button of the wires you removed. If you read your transformer voltage, then the problem more than likely is a faulty doorbell, if not you will need to check your button. If there is a back door button repeat the procedure for testing that button. Mark the other set of wires so you don't mix them up.
Before you begin testing the buttons, remove the low voltage wires from the transformer so you don't damage it. To test the button you will need to remove it and unhook the wires. Set your meter to continuity. Most meters will emit a tone when there is continuity, otherwise you will look for 0 ohms. Attach the meter to the screws on the button and press the button. You should hear the tone or read 0 ohms, if not the button is bad. Perform this same procedure on all other buttons, and replace any that are defective. You should also test continuity on the low voltage cables while you have the buttons out to insure there are no breaks in the wiring.
It has been my experience that most problems lie in either the transformer or the doorbell itself. I have rarely found cut wiring or bad buttons, although it is not uncommon. I suggest focusing on the transformer and doorbell first and then troubleshoot the other components. As always, if you feel unsure or unsafe stop and call a qualified electrician.
ALWAYS BE SAFE!
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