Wired/Wireless Doorbell Only Works Briefly—19VAC at Transformer, Low Voltage at Chime

Please help me figure out an issue.

I built a new home and purchase a wired/wireless doorbell. I had ran the wires during construction. Once I installed the transformer and chime box I noticed that I had 19VAC on the terminals at the transformer and small millivolts at the chime. I checked for continuity and it appeared to not have a short. After trying multiple things, we decided to just pull a new wire.

So we pulled a new wire accessing the wiring from the crawl space. The new wire isn't pinched anywhere and is loose in the wall cavity. I also purchased a new chime just in case it was bad. When reading the new chime box it stated to have 16VAC so I purchased a new transformer that can be wired three ways. 8V, 16V & 24V. Once I installed it and checked with the multimeter it was putting out 10V, 19V & 29V so I decided to use the 10V and see if that would work.

After wiring everything back up, the doorbell worked for a couple hours. Later in the evening I went to test it again and it wouldn't work. So now the wiring at the chime is back to millivolts again, but at the terminals on the transformer it is still 10V!

So I took the wires off and checked continuity and it is good. So I put the wires back on and it is 10.37 VAC at the terminals and 1.4mV at the other ends at the chime.

Can someone please help me understand what is going on here?

Thanks in advance for any insite.

Jim

 

 

 

Hi Jim,

Based on some exp. that are related to this case, low voltage or some low power supplies that travels long wiring has some effect on the operation of the device being supplied, probably the power received is not enough to supply properly the device.

Noise/fluctuation/fault on the device itself that is being supplied is another part to be considered, so better to check or put some grounding on the device.

Ratings and specifications of the device are also important thing to be considered before powering it up.

These are just some of the parts that need to be considered, however, there are more to it especially for custom made doorbell design and wiring.

Hope it helps.

Best,
Neil

Not sure how much expertise you have here but I'll start from basics. You have power available from the transformer. The transformer has 2 terminals,you wire through the 2 terminals of the chime, through the 2 terminals of the switch, like this

Trans A--------------------------------------------------- C
.... / sw
fformer B----F--chime--E------------------------------ D

The transformer terminals are A and B, that's where you are measuring voltage.
The chime terminals are E and F, they will only have voltage on them when the switch is operated (pressed).
The switch terminals are C and D. When you short them out, current (hence power) can flow through the circuit and make the chime sound.


It sounds like your switch may be the problem. With the transformer disconnected, use your multimeter on resistance (200 ohms or 2KOhms range) and measure between the points below while you get someone to press the switch.
Points A and B and you should get less than 500 ohms
Points A and E and you should only get a few ohms (less than 20)

If you don't get similar readings to this, check the switch itself, with nothing else connected to it. with it pushed you should only get a few ohms. With it not pushed it should be open circuit (infinite resistance).

If it does seem like your switch is bad, try shorting its terminals C and D with a short length of wire, that should make the chime sound.

This may seem like I'm assuming you're an idiot, but stranger things have happened to me... . Make sure you have stripped any insulation from the wires before connecting them. if you don't you will get unreliable or non-working connections (which si what you seem to have....

Good luck....

Jim, sorry, the diagram above is not good. I can't post graphics but I tried attaching a JPG file.

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