How two-way switching works
Each two-way switch has three connections: a common, and two others linked to the switch at the other end by a pair of wires, often called strappers. Flicking either switch moves the power from one strapper to the other, so the light changes state from either end. Hallways, stairs and long living rooms with two doors are the usual places for it.
With three or more switches for the same light, an intermediate switch sits in the middle. The principle is the same, with more connections to get right.
Why it stops working
The most common cause is a switch that was recently changed. A new plate fitted with a one-way mechanism, or with the common and a strapper swapped, works from one end only, or only when the other switch is in a particular position. Smart switches and dimmers need a matching secondary unit at the other end, and fitting a single smart switch without one gives the same symptoms.
If nothing has been changed, a loose connection or worn mechanism at either switch, or a damaged cable between them, is the likely cause. A switch that feels warm, crackles or only works if you press it a certain way is worn and should be replaced.
Why it's a job for an electrician
Finding the fault means opening both switches and testing the wiring, and both can be live even with the light off. Energy Safe Victoria says electrical work isn't a DIY job, even for small jobs like changing light switches. Once it's fixed, you get a Certificate of Electrical Safety.
What you can safely do now
- Try the light from both ends with each switch in both positions, and note which combinations work.
- Tell us if either switch has been replaced, or changed to a dimmer or smart switch, recently.
- Stop using a switch that is warm, buzzing, loose or cracked.
Services that can help
Read more in our guides
Related questions
- Why do my lights turn on or off by themselves?Lights that switch on or off by themselves are usually following instructions you've forgotten: a smart switch schedule, a routine in an app, a motion or daylight…
- Why does my light switch buzz or feel warm?A dimmer can hum faintly and feel a little warm, because it is an electronic device that sheds some heat while it works.
- Why do my LED lights buzz or hum?Most buzzing LEDs come from a mismatch rather than a fault: a dimmer built for old halogen globes, an LED driver that doesn't suit the dimmer, an old transformer left in…
- Why do my light globes keep blowing?Globes that fail early usually have help.
Sources for this answer
2 sources, with the date each was checked
- 1.Energy Safe Victoria: Electrical work isn’t a DIY job, even for small jobs such as changing power points or light switches. Accessed 30 September 2026.
- 2.Energy Safe Victoria: Whenever a licensed electrician completes any electrical installation work, they must provide a Certificate of Electrical Safety (COES). Accessed 30 September 2026.
General information for homes in Victoria. Every installation is different, so treat this as a starting point. Where this answer refers to Victorian safety or rental rules, the sources above have the current requirements.