Bathroom Extractor Fan Not Working? Causes and Checks

A bathroom extractor fan that has stopped working is almost always one of four things: a tripped or switched-off fan isolator, a failed timer or humidistat, a seized motor, or a blocked duct. Two of those you can rule out yourself in a few minutes without touching any wiring.

The pattern we see most often is a fan that has been getting louder and lazier for months, a mirror that stays misted long after the shower, then one day silence. By the time it dies completely, the black specks in the silicone have usually already moved in. Catching the fault early is cheaper, and it saves the ceiling.

The five faults behind most dead fans

If you want the short version before the detail, this is how the calls we attend usually shake out:

• Fan completely dead, no sound: isolator switched off or tripped, or a supply fault. Fix: check the isolator and the consumer unit.
• Fan dead only on overrun, or never stops: failed timer or humidistat. Fix: new timer module or new fan.
• Fan hums but doesn't spin: seized motor bearings. Fix: replacement fan in most cases.
• Fan spins but doesn't clear steam: blocked grille, stuck backdraught shutter or a crushed duct. Fix: clean and free the airflow path.
• Fan trips the lights or the RCD: moisture tracking into the electrics or a failing motor. Fix: isolate it and get it tested.

The rest of this post takes each one in turn.

Start with the fan isolator

Most bathroom fans, especially the ones with an overrun timer, are wired with a permanent live, a switched live from the light, and a neutral. Because of that permanent live, the fan needs its own local means of isolation, and the standard answer is a three-pole fan isolator that cuts all three conductors at once.

Here is the part nobody tells you. That isolator usually looks exactly like a normal light switch. It lives above the bathroom door, in the airing cupboard, on the landing wall, or in the loft next to the fan. People switch it off by accident all the time, or a previous owner turned it off years ago and nobody remembers why. Before anything else, find it and check it is on.

Next, the consumer unit. Look for a tripped breaker or RCD and reset it once. Only once. If it trips again with the fan on, that is the fan telling you something is wrong inside it, and repeatedly resetting it just keeps re-energising a fault. Our guide to why a fuse box keeps tripping explains the patterns in more detail.

Timer and humidistat faults

If your fan carries on running after the light goes off, it has an overrun timer, usually adjustable from about one to thirty minutes. The timer is a small electronics module inside the fan, and it fails in both directions. A fan that stops the instant you kill the light, or one that runs for hours, has usually lost its timer. Sometimes the whole fan appears dead because the timer module has failed and taken the switching with it.

Humidity-sensing fans have their own version of this. The humidistat triggers the fan when moisture in the air crosses a threshold. A failed sensor means the fan never comes on at all, or comes on at 3am for no reason and stays on. There is also a far sillier cause: the sensitivity dial, which sits behind the grille on most models. We have attended "broken" fans that turned out to be a humidity dial knocked to maximum when someone cleaned the cover.

One warning before you investigate either. Adjusting those dials means removing the grille, and on a timer fan there is a permanent live in there even with the light off. Isolate at the fan isolator first, or leave the cover on and let us do it.

A seized or failed motor

A fan that hums but doesn't spin is getting power. The motor is trying to turn and can't, because dust and moisture have gummed up the bearings over years. Occasionally a careful clean frees one up. More often the bearings are worn rather than sticky, and the fan is finished.

A completely silent fan with a confirmed supply usually means a burnt-out motor or a dead circuit board. Fan motors are sealed units and nobody repairs them. On a budget fan that has given you eight to ten years, a burnt-out motor is simply the end of its life, and honestly that is a fair innings for what they cost.

The fan runs but nothing comes out

This one fools people because the fan sounds healthy. The quick check is the tissue test: hold a square of toilet paper against the grille while the fan runs. If it sticks there on its own, the fan is pulling air. If it flutters or falls, the fan is spinning but not extracting.

When the tissue falls, work along the airflow path:

• Grille and impeller. Lint and dust mat the grille and cake the impeller blades until they move almost nothing. A clean often restores most of the airflow.
• Backdraught shutter. The small gravity flaps at the fan outlet or the outside grille, there to stop cold air blowing back in. Dust glues them shut and the fan ends up pushing against a closed door.
• The duct. Flexible ducting in the loft gets crushed by stored boxes, kinked round timbers, or fitted far too long so it sags and traps condensation. Any of those strangles the airflow. Worse, we regularly find ducts that have come off the fan spigot entirely, pumping warm wet air straight into the loft, which just moves the mould problem upstairs.
• The external grille. Blocked with cobwebs, moss, or the occasional bird's nest.

One more that surprises people: an extractor fan needs air coming in to push air out. If the bathroom door fits tightly with no gap underneath and the window is shut, a good fan can stall against its own suction. Try the tissue test again with the door open a crack.

Noisy, rattling or humming fans

Noise is the fan's way of announcing the fault early, and the sound tells you a lot. A rattle or vibration is usually loose screws or a warped cover, and tightening things up fixes it. A whistle or roar means the fan is working against a blockage somewhere along the duct. A grinding or scraping noise is worn bearings, and that fan is on borrowed time. And the steady hum with no spin is the seized motor from above.

Most fans get noticeably louder in their last year. If yours has started drowning out the radio, it is worth dealing with before it dies completely, because a planned swap is always easier than an emergency one.

When the fan trips the lights or the RCD

Take this one seriously. If switching the fan on drops a breaker, kills the bathroom lights, or trips the RCD, there is a genuine electrical fault. The usual causes are a motor breaking down and leaking current to earth, or moisture tracking into the connections, sometimes from condensation in the duct and sometimes from rain getting in through a poorly fitted outside grille.

Every circuit in a bathroom is required to have RCD protection, and Electrical Safety First states that "all circuits in or passing through bathrooms or shower rooms are now required to be protected by an RCD". So when the RCD trips on your fan, it is doing exactly the job it is there for. Leave the fan isolated and get it tested rather than resetting and hoping. If you want to understand what the RCD is actually reacting to, our explainer on what an RCD does covers it.

What you can safely check yourself

Bathrooms are treated as a special location in the wiring regulations because water and bare skin raise the stakes on any shock. Approved Document P is the building regulation covering electrical safety in dwellings in England, and our post on bathroom electrical zones shows how close your fan sits to the shower. So the DIY list is deliberately short:

• Find the fan isolator and check it is on.
• Check the consumer unit for a tripped breaker or RCD, and reset once only.
• Listen: silent, humming, or running rough.
• Do the tissue test, with the door open and closed.
• Look at the outside grille from the ground for obvious blockage.

Everything past that list involves live conductors a few feet from water. Removing the grille, adjusting the timer or humidity dial, and any wiring work starts with isolating and proving dead, and if that sentence makes you hesitate, it is a job for us. Our fault finding and repairs service exists for exactly this kind of job.

A dead fan is a damp problem on a timer

It is tempting to live with a broken fan, especially in winter when opening the window feels like punishment. The trouble is that every shower puts a kettle's worth of moisture into a small sealed room, and without extraction it goes into the grout, the silicone, the ceiling paint and eventually the plaster.

The government takes this seriously enough to have published dedicated guidance for rented housing on the health risks of damp and mould, which links prolonged mould exposure to respiratory conditions. If you rent and your fan has died, that guidance is worth pointing your landlord at, because a working extractor is part of the fix.

Ventilation rates for bathrooms are set by the Building Regulations through Approved Document F, which is why bathroom fans are designed around an intermittent extract rate of about 15 litres per second. The full rules, including when a fan is required at all, are in our post on bathroom extractor fan regulations. The short version: if your room has a fan, it needs that fan working.

Repair or replace

A rough rule from doing these every week. If the fault is the isolator, the wiring, the timer or the ducting, repair wins every time, because the fan itself is fine. If the motor or bearings have gone on a basic fan, replacement is usually the sensible call, because the labour to strip a cheap motor costs more than a new fan.

Replacement is also the moment to upgrade. A like-for-like swap can become a quiet humidity-sensing model for not much more, and a decent fan moving the proper amount of air makes a visible difference to a bathroom within a fortnight. As a rough guide, the typical UK market cost of supplying and fitting a replacement bathroom fan sits somewhere between £100 and £250 depending on access and the fan you choose. Costs vary with every job, so get a fixed quote before anyone starts.

Frequently asked questions

Why has my bathroom extractor fan suddenly stopped working?

Most often the fan isolator has been switched off or the RCD has tripped, both of which take a minute to check. After that, the likely causes are a failed timer module or a burnt-out motor. Work through the checks in order before assuming the worst.

Why is my extractor fan humming but not spinning?

Power is reaching the motor but the bearings are seized, usually from years of dust and moisture. A clean occasionally frees one, but a humming fan that won't turn normally means a replacement.

Why does my bathroom fan run but not clear the steam?

Do the tissue test. If the paper won't stick to the grille, the blockage is somewhere along the airflow path: a clogged grille, a stuck backdraught shutter, or crushed flexible ducting in the loft. A tightly sealed bathroom with no gap under the door can also starve the fan of air.

Why does my extractor fan keep running after the light goes off?

That is the overrun timer doing its job, clearing moisture for up to about thirty minutes after you leave. If it runs for hours or never switches off at all, the timer or humidistat has failed and needs replacing.

Can I replace a bathroom extractor fan myself?

It is not a good DIY job. The fan sits in a bathroom zone near water, a timer model carries a permanent live even with the light off, and the electrical work has to meet the building regulations. An electrician can swap one in under an hour in most cases, with the right tester to prove the circuit is dead first.

How long should a bathroom extractor fan last?

A budget fan typically gives you around eight to ten years. Better-built models run longer, and any fan lasts longer if the grille and impeller get cleaned every year or two rather than never.

Fan dead, humming, or just moving noise rather than air? We'll find the actual fault and tell you honestly whether it needs a repair or a replacement. See our extractor fan installation service or call 020 3653 2600 for a straight answer and a fixed quote.