Why has my wired doorbell stopped working?
The four-part chain a wired doorbell depends on, tested in the order that finds the fault fastest, and where the extra-low voltage work stops and mains work begins.
- Difficulty
- beginner
- Time
- 30 min
- Read
- 5 min
- Safety
- caution
Short answer
The chain is transformer, bell push, wiring, chime. Test the chime by bridging the two bell wires at the push — if it sounds, the push is faulty and is a two-minute replacement. If it does not, suspect the transformer, which is the commonest failure, or a broken wire. Everything on the bell side is extra-low voltage; the transformer's mains side is not yours.
A traditional UK wired doorbell runs on 8V or 12V from a small transformer, usually mounted next to the consumer unit or in a cupboard, and often fed from a fused connection unit or from a spare way in the board. Because it is extra-low voltage, most of the fault-finding is genuinely safe — which makes it one of the few electrical faults a householder can chase properly.
Safety
Step by step
- Find the transformer.Look next to or under the consumer unit, in the meter cupboard, in a hall cupboard, or occasionally in the loft. It is a small box, often with 4V, 8V and 12V terminals marked, fed by a mains cable and with two thin bell wires leaving it.
- Check whether it has power.Many transformers have an indicator. Otherwise, check whether the circuit or fused spur feeding it is on — the fuse in a fused connection unit feeding a doorbell is a very common and completely silent failure point. Switch the spur off, and only then, with it isolated, check the fuse.
- Test the bell push by bridging it.Remove the bell push cover — two small screws — and briefly touch the two wire ends together, or the two terminals. If the chime sounds, the push is the fault. This is safe because it is extra-low voltage.
- Replace the push if that was it.Bell pushes corrode, especially unlit ones on a north wall. A new push is inexpensive, wires to the same two terminals in either orientation, and takes minutes. Fit one with a rubber gasket if the door is exposed.
- Test the chime if bridging did nothing.Open the chime unit. If it is a mechanical chime with solenoids and bars, look for a stuck plunger, a fallen bar, or a corroded terminal. If it is electronic, check any battery it may contain — some units are battery-backed for the chime and mains-powered for something else.
- Suspect the transformer next.Doorbell transformers fail, often after years of continuous energisation. There is no owner-level test without a meter, and no owner-level repair. Replacing one means mains work and it belongs to an electrician unless it is a plug-in type.
- Consider the wiring last.Bell wire runs are usually stapled along skirting or through the loft. Breaks happen where the wire passes a door frame, where it has been stapled through, or where it enters the wall outside. A visible break is easy to see; an invisible one needs continuity testing.
- Consider a wireless replacement if the wiring is the problem.If the fault turns out to be a broken run in a wall, a battery wireless chime and push is far cheaper than chasing the cable, and no electrical work is involved at all. It is a completely legitimate answer.
Tips
- Note the transformer's output voltage before buying a replacement chime — an 8V chime on a 12V supply will be loud and short-lived, and a 12V chime on 8V will be feeble.
- Corroded bell push terminals often just need the wire ends snipped back to clean copper and re-terminated.
- If you are thinking of a video doorbell, check its transformer requirement first — many need more current than an old bell transformer can supply.
Common mistakes
- Opening the doorbell transformer to investigate — One side of it is mains. There is nothing serviceable inside and nothing an owner needs to see there.
- Assuming the chime is broken because it is silent — The push is the most exposed component and the transformer is the most likely to have aged out. Bridging the push tests two thirds of the chain in one action.
- Fitting a video doorbell to an old bell transformer without checking — Video doorbells draw far more than a mechanical chime and often specify a minimum VA rating. An underpowered transformer produces intermittent, maddening faults.
If it doesn't work
Bridging the push wires sounds the chime
Cause: Faulty or corroded bell push — Fix: Replace the push. Two screws and two terminals.
Bridging does nothing, chime is a mechanical type
Cause: Transformer, wiring or chime mechanism — Fix: Check the fused spur feeding the transformer, inspect the chime mechanism for a stuck plunger, then suspect the transformer.
Chime buzzes continuously
Cause: Bell push stuck closed, or a short in the bell wiring — Fix: Disconnect one wire at the push. If the buzzing stops, the push is stuck. If it continues, the wiring is shorted somewhere.
Chime sounds weakly or only one note
Cause: Low supply voltage, wrong transformer tapping, or a seized solenoid — Fix: Check which output terminal the bell wire is on. A mechanical chime with one working note usually has a stuck plunger, freed with a careful clean.
Worked until the electrics were worked on
Cause: The fused spur feeding the transformer left off, or its fuse removed — Fix: Check the spur and its fuse. This accounts for a surprising number of "suddenly dead" doorbells.
Questions people ask
Is the bell wire dangerous?
The bell wire itself carries 8V or 12V, which is extra-low voltage and safe to handle. The transformer's input side is mains and is not. Never assume a wire near a consumer unit is a bell wire because it is thin.
Can I fit a new transformer myself?
If it is a plug-in transformer, yes — it is an appliance. A hard-wired transformer connected to a fused spur or mounted in the consumer unit is mains work, and consumer unit work in particular is not owner work at all.
Why does my doorbell work sometimes?
Intermittent almost always means the push, where water and corrosion get in, or a bell wire chafing at a staple or a door frame. Start with the push.