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My house was built in 1982. I moved in over a decade ago but never bothered to fix the non-functioning wired doorbell. I’m trying to diagnose it now to see if it’s worth trying to fix or if I should just let it go and maybe get a wireless one instead. I used a low voltage tester on the transformer in my basement and the tester lit up so it appears the transformer is working. However, when I tested both the outside lead wires by my front door and also the wires in the doorbell chime unit (NuTone KA-10), I’m not getting anything. What does this indicate and how involved is the fix? Do I need new wiring and if so, does that require following the wire all through my house and knocking out drywall? If so, I think I’ll pass on it. Thanks in advance.enter image description hereenter image description hereenter image description hereenter image description here

  • It could be "anything". What voltage do you measure on the transformer? Are you sure it is for the doorbell and not the thermostat or something else? – manassehkatz Dec 13 '18 at 2:47
  • @manassehkatz the voltage is measuring 13.2V. I assumed it’s for the doorbell since it’s the only transformer I’ve seen (it’s located below the breaker box). There is a red and a white wire coming out of the transformer which combine into one – Dave Dec 13 '18 at 2:56
  • That does look like it could be a doorbell transformer and 13.2 V is closer to typical doorbell than to typical HVAC. The next step is to trace the wires and look for a break. – manassehkatz Dec 13 '18 at 4:24
  • @manassehkatz how would I go about doing that? Do I need an electrician or is it something a newbie could attempt? So since I’m seeing voltage at the transformer and no voltage at the chime unit then there’s a break in the wire somewhere? Thanks for clarifying. – Dave Dec 13 '18 at 4:29
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    @manassehkatz wow, that's wild. so you would use that to try and trace the wire through the drywall. How would I even know what path the wire takes though? All I know is that I can see the combined wire go up somewhere above my circuit breaker panel on the backside of my house and somehow end up coming out of the wall near the front of my house where the chime unit was mounted. Thanks for the insight – Dave Dec 13 '18 at 16:26
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The problem could be the button, the chime, the transformer (tested OK), or the wiring in the walls. Check the devices before chasing wires through walls. Start with the front button: disconnect and touch the 2 wires together. Does it ring? Then put your voltmeter on the chime coil. Does the chime get voltage when you touch the button wires together? If you have voltage at the chime with no bing-bong, then the chime is faulty. The only time you should measure voltage at the chime is when the front button is pushed. If it rings only when you touch the wires, then the front button is faulty.

  • I took the front button off a long time ago. When I touch the 2 wires together from near the front door, nothing happens. I tested the wires that go into the chime but I'm not getting any voltage there. I don't think I've tried touching the 2 wires from the front button together and then testing for voltage on the wires going into the chime...is that what you're saying I should test? Thank you. – Dave Dec 13 '18 at 16:29
  • Open the chime cover. Chimes usually have 2 coils: a bing-bong for the front door, and a bing for the back door. There will be 3 terminals inside the chime, A B C, with A the front coil, B the common, and C for the back door. Mark and remove the wires on the terminals to check the continuity (ohms) of each coil. The coil resistance should be between 100 and 400 ohms. If you have voltage (while pushing the button) and you have continuity, then the plunger could be stuck. The plunger should slide easily between the return springs. Clean it with alcohol or electrical contact spray, not oil or WD. – John Canon Dec 14 '18 at 2:25
  • I just posted a pic of the chime. I removed the wires to it. There was one red going to the trans. (Middle one) and the front (terminal on the right). There were also two white wires that were connected to each other with a wire nut. I just bought a multimeter...how do I test continuity of each coil? I’ve never tested the voltage of the wires going to the chime while holding the leads together that go to the button...is that what I need to do? – Dave Dec 14 '18 at 2:51
  • Set your multimeter (DMM digital multimeter) to ohms. Put the test leads onto TRANS and FRONT. Note the ohms resistance. Reading should be between 50 and 500. Then check ohms on the TRANS and REAR terminals. A super high reading means there is a break in the coil wire. In your picture, the solder joint at FRONT looks like it is breaking apart. Heat up a soldering iron and quickily remelt and add a touch of solder with flux. You can also unbend the 3 tabs and lift out the board with both coils.. Broken wires usually occur near the terminals rather than inside the coil. You are getting closer. – John Canon Dec 14 '18 at 6:06
  • You can also do the chime voltage test while the button wires are twisted together. Since you already have the wires off the chime, do the continuity tests first. – John Canon Dec 14 '18 at 6:09
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You can purchase an electrical wire tracer and follow the wire through the house. This is also useful for figuring out if there are any breaks in the wire.

You can also test the voltage differences at the doorbell -- might be a bad doorbell, not a bad set of wires.

Easiest way to test this is to get a coil of wire and use it to test continuity each of your transformer->doorbell wires individually.

  • So with the wire tracer, I would try and trace the wire though the drywall? I have no idea the path it goes though..how are those used? I have tested the leads on the wires at the front door and don't get any voltage. Can you clarify what you mean by getting a coil of wire and doing a continuity test (sorry, i'm a newbie). I recently bought a multimeter so I'm assuming that I can use that to do the testing – Dave Dec 13 '18 at 16:32
  • diy.stackexchange.com/questions/74729/… I used the electrical tracer by attaching it to the transformer wire and walking around the house looking like harry potter waving a wand. I eventually figure out a rough idea of where the wires went. To do a continuity test, you need a known good wire, so you can attach a long one to your transformer and drag it out to the doorbell. You can also use a multimeter as well-- look at the voltage difference between the wires. – gbronner Dec 15 '18 at 21:36
  • I seem to be getting 0v everywhere except the transformer (13.2v instead of the full 16). I was trying to avoid becoming Harry Potter to solve this but is it your hunch that there is a break or cut in the wire somewhere? I’m trying to avoid having to pay an electrician or going wireless – Dave Dec 16 '18 at 0:13
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I don't trust anything other than a volt meter with low voltage because some are AC and some are dc. I have been fooled in the past with high end low voltage detectors. In my experiance the wiring is usually ok if it worked. The main problems I have found is bad switch or contact to the switch #1. The next check I have found is at the chime it self, many electronic chimes don't last long for my #2 problem. The more rare problem that I have found is the transformer has failed , for me this has happened 2x on on a Victorian home with a ceramic encased transformer and another with a 60's era transformer as #3. The last and number 4 issue was a residing company drove a staple through the twisted wire that shorted them together, the chime was connected all the time so it buzzed, the owner had replaced the transformer and switch prior to calling me. Found the shorted wire and pulled new wire then good to go. These are the problems I have found ( well other than a few tripped breakers for other reasons) so these would be the areas I would check. Some electronic chimes have back up batteries when the 9v battery died and actually dragged the chime voltage down it failed to work so there quite a few simple things to check. Added: since you have a simple chime unit this should not be hard. Your voltage is a bit low but I would expect it to work. My first test would be to disconnect the door bell switch and take a measurement, also short the 2 wires together by hand if the chime activates bad switch, you should see a voltage similar at the switch location, I suggest removing the switch from the circuit because lighted switches that have failed have provided strange readings. Verify the wiring a wire may have come off at the chime or transformer. I have found bad coils in chime units but this has been less often and I have not had both coils fail measuring the chime coil resistance should provide a resistance value on both coils if open the coil is bad. I had already had mentioned the wiring to the chime and and switch so this is all there is to test.

  • Thanks for the reply. The voltage meter reads 13.2V when I put a probe on each of the 2 screws holding the wires. The transformer has 2 wires coming out of it (red and white) which then combine into one. There are 2 white wires and 2 red wires coming into the chime itself (from hole in wall near front door). – Dave Dec 13 '18 at 3:05
  • So this is a 12v chime? Some are 24v just want to know the transformer value and chime rating, the 2 wires if other than the transformer could be front door / back door if either switch is bad it could cause problems, what kind of chime? – Ed Beal Dec 13 '18 at 3:17
  • I can’t tell because I can’t get my head under the transformer because of shelving located under the breaker box. I was able to take a picture of it and post it in my original post. I can’t make it out well but I can see it’s an Edwards transformer and the number at the bottom looks like 88080 or 88090 and it says class 3 wet, class 2 not wet. – Dave Dec 13 '18 at 3:48
  • I may have misunderstood your question- the chime is a NuTone KA-10. Not sure the volts...after doing some googling, maybe 16v? – Dave Dec 13 '18 at 4:21
  • It looks like 16 v is correct 30va looks to be the most common size. I would expect the unloaded (not trying to fire the bell) to have a slightly higher voltage at the transformer. – Ed Beal Dec 13 '18 at 15:02

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