Why does my bathroom extractor fan keep running?
A bathroom extractor fan that carries on after you switch off the light is often working exactly as intended. Many fans have an overrun timer or humidity sensor so they can keep removing moist air. If it runs for hours, never stops, or has suddenly changed behaviour, it may need checking.
An overrun timer may be doing its job
Timer fans commonly continue for a set period after the light or fan switch is turned off. This helps clear steam that remains after a shower or bath. The run-on time varies by model and may be adjustable, so the manufacturer's instructions are the best place to check what is normal.
Time it from the moment the light goes off. If the fan stops consistently after several minutes, the overrun is probably intentional rather than a fault.
A humidity sensor can keep the fan on
A humidistat fan responds to moisture in the air. It can start or continue running even when the light is off, then stop when humidity falls below its setting. Long showers, wet towels, drying laundry and poor replacement airflow can all make this take longer.
Open the bathroom door after use if it is safe to do so and keep air inlets clear. Do not cover the fan grille or permanently switch off useful ventilation just because the sound is inconvenient.
Check the switches without opening anything
Some bathrooms have a separate fan switch as well as a light switch. There may also be a three-pole isolator near the bathroom for maintenance. Check whether an ordinary wall switch has been left on, but do not use a maintenance isolator as the everyday control unless your installer says it was designed that way.
Do not remove the fan cover or attempt wiring adjustments. Bathroom electrical work has extra safety requirements and should be handled by a competent electrician.
When might constant running indicate a problem?
A fan that never stops in a dry room may have an overly sensitive or dirty humidity sensor, an incorrectly adjusted timer, a sticking control, or a wiring fault. A blocked duct or weak airflow can also leave moisture around for longer, although the motor may still sound as if it is running normally.
Arrange an inspection if the behaviour changed suddenly, the fan runs continuously, or it no longer responds as expected. Stop using it and isolate the circuit only if it is safe to do so if you notice a burning smell, scorching, crackling or unusual heat, then contact an electrician promptly.
What if the fan is simply too noisy?
Constant awareness of the fan can make a normal overrun feel excessive. Dust on the external grille, worn parts, vibration or a restrictive duct can increase noise. Cleaning only the accessible surface in line with the manufacturer's instructions may help; internal cleaning, replacement or electrical adjustments should be left to a suitable professional.
Quick fan checklist
- Time how long the fan runs after the light goes off.
- Check whether it stops once the room has dried.
- Look up whether the model has a timer or humidity sensor.
- Make sure an ordinary fan switch has not been left on.
- Keep the grille and replacement-air path unobstructed.
- Call an electrician if it never stops or shows electrical warning signs.