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First time posting but hoping for some help as I haven't been able to solve this yet. I have a new construction home (2 years old) and, out of the blue, an AFCI breaker tripped when turning on a light switch in a bedroom which controls a ceiling fan / light combination. There was was also a loud-ish buzzing sound in the wall for a few seconds and the trip happened immediately. I flipped the breaker back on and saw an arc fault light on. When I tried turning the switch on again, the same thing happened again.

My first thought was that it might be the fan. Although it is new, I checked it and it was spinning freely. Nevertheless, I completely removed the wiring from the fan so that it was no longer connected to the circuit. Unfortunately, the breaker still tripped immediately when flipping the switch and I still heard the buzzing sound.

My next test was to replace the wall switch itself but that did not yield any different results and the buzzing sound still persisted.

On the same circuit is a bathroom exhaust fan as well as a ceiling fan / light in another bedroom, neither of which have any issues. Outlets on the same same circuit do not have any issues either. I had nothing plugged in when testing the above.

I have been trying to schedule with an electrician but have not been able to get anyone out yet for something small like this so am still hoping to get this resolved on my own in the interim. I don't have any electrical tools to troubleshoot and try and find a potential issue so guidance on what would be needed and what to look for would be very helpful!

Thank you! Pamela

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  • Is the buzzing sound at the switch or away from the switch inside the wall? At the switch should be easy, the switch is too close to the metal box or a ground wire. Inside the wall, a new nail/screw, cable is pinched, mice. Repairing drywall is easy, matching paint is hard. If lucky a good place for a picture till repaint of the wall.
    – crip659
    Jan 5 at 23:01
  • @crip659 It's not directly at the switch but seems to be somewhere in the room. I can't locate it exactly as it only lasts about 1-2 seconds before the breaker trips. Perhaps it is something to do with a cable somehow (either rodents or otherwise). What is the best way to figure out where exactly it's coming from since I don't have much time before the breaker trips? I don't exactly want to keep doing it over and over just trying to locate the spot. Can I also try to pull the cable out instead?
    – Pamela
    Jan 5 at 23:50
  • The switch and the fan will be the easiest to check for hot/live being too close to metal box or a bare wire too close. Cables inside walls are usually stapled/attached to the studs(possible pinch points), so might need an inspection camera(only needs small holes) to see inside the walls. Any work on the wires/connections needs to be done with the breaker off. You do not want to find power with your fingers.
    – crip659
    Jan 6 at 0:12
  • Welcome to the site Pamela. Please merge your accounts so you have access to edit, comment, and accept answers on your own question. Note that posting responses as answers can result in an automated lock that can prevent others from assisting you.
    – BMitch
    Jan 6 at 16:45

1 Answer 1

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  1. You have an arc fault breaker
  2. You heard a buzzing noise in the wall
  3. The breaker indicated an arc fault

Congratulations, you have an arc fault, probably in the wall where the buzzing was heard. Your arc fault breaker is doing its job preventing your house from burning down. Find and fix the arc fault. It's probably near where you hear buzzing. Meanwhile, don't use the circuit in question until it's fixed.

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  • Thank you for your response! Sorry if this question sounds super basic why would I suddenly have a fault, especially on a new build? There was nothing new done and I hopefully don't have any rodents (but who really knows). Would wires suddenly fray? And would the fix be to re-run the wires?
    – Pamela
    Jan 5 at 23:32
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    @Pamela One possible scenario is that a plastic-insulated cable in the wall is pinched by a metal cable staple. It could happen that the pressure exerted by the staple finally succeeded in breaking the plastic insulation and now there's electrical contact between the cable and the staple.
    – Greg Hill
    Jan 6 at 0:14
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    @Pamela It might be under the builder's warranty. I would check first before punching holes in the walls. Usually a house has five years, more or less.
    – crip659
    Jan 6 at 0:16
  • Builder electricians like to use push-in “backstab” terminals on switches and receptacles. They’re faster than using the screws, but notoriously unreliable - known for failing exactly this way. They’re a large part of the reason why the NEC mandates AFCI now.
    – nobody
    Jan 6 at 1:34
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    @Pamela There might be a scent in the vicinity of the arc (electrical arcs may have an ozone smell, or burnt electronics if it's a coil, or wood when things are very bad). One reason the symptom may appear sudden is that it can take a while before enough material burns away to make a gap wide enough to buzz/trip. As others have said, it's best not to use the circuit until you isolate and know/fix the cause. Also, check that the bulbs are tightly connected.
    – RG Hughes
    Jan 6 at 1:55

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