Hey everyone! I have this charming old mercury switch doorbell that I've been using with a new Nest doorbell as my chime. It's been running fine for about two years with a 24V transformer. Recently, the Nest doorbell lost power, so I checked the chime by connecting the bell wires, and it made a half-sound (just a "ding"), but no "dong," and now the doorbell unit is buzzing with the mercury switch stuck open. If I turn off the power at the RCD, it releases, but as soon as I switch it back on, it gets stuck again. Has anyone experienced this before? Should I try to diagnose it myself or just call an electrician? For reference, I've left it off for now and have a video I can share if needed! Thanks for any help!
3 Answers
Definitely sounds like you have a short circuit problem. When I installed a doorbell, I once drove a screw too far and shorted out the system, leading to the same issue—just a ding sound. Once I stopped the power, it resolved, but it took replacing the wires to fully fix it. Double-check your wiring, especially with how old your system is!
As someone who's fixed a few of these, I can tell you that if you're only getting a "ding" and not a "dong," it might mean there's a short somewhere. The solenoid should push the clanger away when power stops, so if it’s stuck, it could damage the unit. I suggest checking the button and wires for issues. Just don’t keep the system powered like this for too long, or it might ruin the solenoid!
It sounds like the buzzing is due to the hammer being stuck against the bell. Often in these old setups, there’s a relay that’s supposed to stop the electrical connection, but it might be malfunctioning. If the doorbell unit constantly sends power, it can cause damage over time. I just had a similar situation with a neighbor—her system got fried because the city messed with the wires. Make sure all connections are secure and consider whether the old bell can handle the power from the Nest. Good luck!
Thanks for the insight! I followed the Nest wiring instructions, but considering how old the doorbell is, I might have caused problems in the long run. I’m thinking about connecting the Nest directly to the transformer to see if that helps.