Doorbell or intercom not working
A wired doorbell or intercom doesn't chime/respond — points at the button, the transformer/supply, the chime/unit, or the wiring.
Safety first
Wired doorbells usually run from a low-voltage transformer, but the transformer's supply side is mains — isolate before working on it.
Isolate, lock out / tag out, and prove dead before working unless a live test is specifically required, authorised, and carried out under proper supervision. Always follow local regulations, your site procedures, and the equipment manufacturer's documentation.
Full detail — causes, the why, and common mistakes.
Likely causes
Ranked from most to least likely.
- 1
Faulty push button
Most likelyThe doorbell button (often outdoor, weather-exposed) has failed or corroded.
- 2
Transformer / power supply failed
#2The bell transformer or plugpack supplying the system has failed or lost supply.
- 3
Chime / intercom unit fault
#3The chime or intercom unit itself has failed.
- 4
Wiring fault (weather-exposed runs)
Least likelyCorroded or broken wiring, especially on the outdoor button run.
Reports are saved on this device to reflect what you actually find.
Testing sequence
Work through one test at a time. Expected reading and what each result means.
Test the button (bridge/replace) and confirm the transformer/supply is providing power.
Button operates; transformer/supply powered.
Button and supply fine — suspect the chime/unit or wiring.
Faulty button or dead transformer/supply — rectify.
View all expected readings at once
Fault-finding flowchart
The same logic as a decision tree.
- 1start
Doorbell/intercom dead
→ step 2 - 2decision
Does the button operate and is the transformer/supply powered?
Yes→ step 3No→ step 4 - 3decision
Is the chime/unit and wiring sound?
Yes→ step 5No→ step 6 - 4result
Faulty button or dead transformer/supply — rectify.
- 5result
Re-check button/supply path.
- 6result
Faulty unit or corroded/broken wiring — rectify/replace.
Common mistakes apprentices make
- Overlooking a corroded outdoor button.
- Forgetting the bell transformer/plugpack can fail.
- Not checking the weather-exposed button wiring.
- Working on the transformer's mains side without isolating.
When to stop & escalate
Mains-side transformer/supply work is licensed electrical. Smart/video doorbells may also need network setup beyond the wiring.
If you're past your competence, authorisation, or the safe limits of the job — stop and hand it on. There's no fault worth getting hurt over.
Related faults
Outdoor / garden light not working
An outdoor or garden light is out — could be the lamp, a sensor/timer, weatherproofing/water ingress, or the supply.
Smart switch not working (no neutral at the switch)
A smart/Wi-Fi switch won't power up, drops offline, or makes the light glow/flicker — commonly because there's no neutral at the switch, which many smart switches need.
Power point (GPO) completely dead
Nothing plugged into a power point works, while other outlets are fine. A classic trace-it-back fault on a single GPO or the run feeding it.