Bathroom/laundry exhaust fan not working
An exhaust fan won't run, runs weakly, or keeps running — common causes are the switch/timer, a seized/dusty motor, or supply.
Safety first
Isolate before working. Bathroom fittings must be suitable for the zone and weather/moisture conditions.
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
Switch / timer / humidity-sensor fault or setting
Most likelyA faulty switch, run-on timer, or humidity sensor stops it running (or keeps it running).
- 2
Seized or dust-clogged motor
#2Dust and lint seize or slow the small motor.
- 3
No supply / shared light-fan circuit fault
#3Lost supply, or a fault on a combined light/fan unit.
- 4
Failed motor
Least likelyThe motor has burnt out.
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.
Check the switch/timer/sensor and that the fan has supply; identify if it won't start or won't stop.
Working control and supply present.
Control/supply fine — check the motor (seized/clogged).
Faulty switch/timer/sensor or no supply — rectify.
View all expected readings at once
Fault-finding flowchart
The same logic as a decision tree.
- 1start
Exhaust fan not working
→ step 2 - 2decision
Is the switch/timer/sensor working and supply present?
Yes→ step 3No→ step 4 - 3decision
Is the motor/impeller free and clean?
Yes→ step 5No→ step 6 - 4result
Faulty control or no supply — rectify.
- 5result
Re-check control/supply path.
- 6result
Seized/clogged or failed motor — clean/replace.
Common mistakes apprentices make
- Overlooking a run-on timer (fan 'won't turn off' by design).
- Not cleaning a dust-clogged impeller/motor.
- Assuming the motor when the switch/timer is at fault.
- Fitting a fan unsuitable for the bathroom zone.
When to stop & escalate
Exhaust fan and switch/timer work is licensed electrical. Combined light/heat/fan units and ducting may need more involved rectification.
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
Ceiling fan not working
A ceiling fan won't run (light may still work, or not) — pointing at the wall control/remote, the capacitor, the motor, or the supply.
Rangehood fan or light not working
A rangehood's fan won't run or its light is out — could be the supply, switches, motor, or (for ducted units) the controls.
A single light not working
One light fitting is dead while the rest of the lights on the circuit work fine — points at the lamp, the fitting, or the switch for that point rather than the whole circuit.