Summary

A fan that's still running but noisy is a different diagnosis from a fan that's stopped altogether — this guide is the noise/vibration-specific companion to the broader extractor fan not working fault tree, which covers dead fans, weak airflow, and wiring faults. Here the fan is doing its job (air is moving) but something is physically wrong with how it's doing it, and the fault almost always traces back to one of a small number of mechanical causes: something loose, something fouled, something worn, or something out of balance.

Noise complaints matter more than they might seem on the surface. A rattling or resonating duct at 2am is one of the most common "nuisance noise" call-outs in a house, and a fan that's started grinding on worn bearings is usually within weeks of total failure — catching it early turns a planned replacement into a same-visit job instead of an emergency call-out when it seizes completely. The diagnostic approach here mirrors the structured logic used for the closely related shower pump noisy vibrating fault tree: isolate mechanical transmission (is the noise coming from the fan itself or from something it's touching) before assuming the fan unit needs replacing.

This article covers bathroom and kitchen extract fans specifically — intermittent (switch/humidistat-triggered), dMEV (continuous decentralised), and centralised MEV systems all share the same mechanical failure modes covered here, though access and isolation procedure differ slightly by fan type. For dead-fan and weak-airflow diagnosis, see extractor fan not working and extractor fan.

Key Facts

Quick Reference Table

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Symptom Most likely cause Field check Fix
Rattling, worse when fan runs, quietens if you press the housing Loose fixing screws / bracket Check fan body and grille fixings by hand while running (isolate first for hands-on checks) Retighten fixings; replace stripped screw holes/plugs
Low hum/wobble, airflow still OK, gets worse gradually Impeller fouled with dust/grease Isolate, remove grille, inspect blade for visible build-up Clean blade per manufacturer instructions, rebalance by cleaning evenly
Grinding or high-pitched whine, worsening over weeks/months Bearing wear Listen close to motor housing; note if noise persists at idle/coast-down Replace fan unit — bearings not serviceable
Rattling sound traced to the duct run, not the fan body Ducting resonance / loose clips Follow duct by hand/ear from fan to grille, check jubilee clips and support Re-clip/secure duct, add insulating wrap to dampen resonance against joists
Fan wobbles visibly at speed, especially on boost Unbalanced/damaged impeller Isolate, visually inspect blade for chips, warping, bent tips Replace fan unit — blade not a serviceable/repairable part
Rattle only on windy days, fan silent when not running External grille flap loose Inspect outside grille for a loose or worn flap Replace/secure external grille
New fan noisy immediately after install Poor fixing or fouled duct during install Recheck all fixing screws and duct connection for pinching/contact Correct fixing/duct routing; check for manufacturing defect if fixings are fine
Noise louder in an adjoining room than at the fan itself Vibration transmitted through rigid mounting Check for direct rigid contact between fan casing and structure Fit anti-vibration mounting/isolation pads if fan design allows

Detailed Guidance

Safety first — isolation before any hands-on inspection

Before touching the fan body, removing the grille, or inspecting the impeller:

  1. Identify the isolator — for a bathroom fan, the triple-pole isolator (a 3-pole rotary switch typically outside the bathroom, in the loft, or in an airing cupboard).
  2. Switch off at the isolator.
  3. Verify dead with an approved voltage indicator before opening the fan cover.
  4. Only listen to the fan running (for diagnostic purposes) with the cover in place and hands clear — do not run the fan with the impeller exposed to touch it while spinning.

Decision tree

Extractor fan noisy / vibrating — start here
│
├── Isolate fan, verify dead, before any hands-on inspection
│
├── Where does the noise/vibration seem to come from?
│   │
│   ├── The fan housing itself, at the wall/ceiling
│   │     │
│   │     ├── Rattles, quietens when you press the housing firmly
│   │     │     → loose fixing screws / mounting bracket
│   │     │       → retighten; replace stripped wall plugs if the
│   │     │         housing won't sit tight against the surface
│   │     │
│   │     ├── Low hum / wobble at running speed, gets worse over weeks
│   │     │     → impeller fouled with dust (bathroom) or grease (kitchen)
│   │     │       → isolate, remove grille, inspect and clean blade per
│   │     │         manufacturer instructions
│   │     │
│   │     ├── Visible wobble at speed, worse on boost/high setting,
│   │     │     blade shows chips/warping/damage on inspection
│   │     │     → unbalanced or damaged impeller
│   │     │       → replace fan unit (blade not repairable/serviceable)
│   │     │
│   │     └── Grinding or high-pitched whine, worsening over time,
│   │           persists briefly after switch-off (coast-down)
│   │           → bearing wear
│   │             → replace fan unit — bearings not field-serviceable
│   │               on almost all domestic fans; lifespan typically
│   │               8-15 years, this is often the final-months symptom
│   │
│   ├── The ducting, traced away from the fan body
│   │     │
│   │     ├── Rattle follows the duct run, worse at bends/joints
│   │     │     → loose jubilee clips or unsecured duct support
│   │     │       → re-clip joints, add/secure duct hangers at
│   │     │         appropriate intervals along the run
│   │     │
│   │     └── Resonance/buzz where duct contacts a joist or the fan
│   │           housing itself
│   │           → duct touching structure and vibrating against it
│   │             → reroute slightly for clearance, or wrap/isolate
│   │               the contact point with insulating tape/sleeve
│   │
│   ├── The external wall grille, only noticeable in wind or when
│   │     the fan is off
│   │     → loose or worn flap on the outside grille
│   │       → replace or re-secure external grille
│   │
│   └── Noise is audible in an ADJOINING room more than at the fan
│         itself
│         → vibration transmitted through a rigid mounting into the
│           building structure
│           → check for direct rigid contact, fit anti-vibration
│             mounting/isolation pads if the fan design supports it;
│             on continuous-running dMEV units this is worth checking
│             first since they run 24/7 and low-level transmitted
│             vibration is more noticeable at night
│
└── Fan is BRAND NEW and noisy immediately after install
      → recheck fixing screws and duct connection first (poor
        installation is more common than a defective unit)
        → if fixings and duct routing are confirmed correct and the
          noise persists, treat as a possible manufacturing defect
          and raise with the supplier/manufacturer

Loose fixing — the most common and easiest fix

Vibration from normal fan operation gradually works fixing screws loose over months and years, especially where the fan is mounted into plasterboard with standard wall plugs rather than a solid fixing. A fan that's developed a new rattle after years of quiet running, with no change in airflow performance, should have its mounting fixings checked before anything else is suspected. Isolate, remove the grille, and check by hand (with the fan off) whether the housing itself is fully secure against the wall or ceiling — any give or looseness at the mounting points is very likely the entire cause. If the wall plugs have stripped out of a soft or damaged ceiling/wall substrate, replace with a heavier-duty fixing rather than just re-driving the same screw into the same worn hole.

Impeller fouling — the gradual-onset fault

Unlike a sudden mechanical failure, fouling builds gradually: a fine layer of bathroom dust, or kitchen grease and airborne cooking residue, accumulates unevenly across the blade surface. Because it rarely builds perfectly evenly, the accumulated mass throws the blade slightly off balance, which shows up as a low hum or gentle wobble that gets progressively worse over weeks or months as more material builds up. Isolating and removing the grille to inspect and clean the blade (following the manufacturer's cleaning guidance — most modern fan blades can be wiped down or, on some models, the whole impeller assembly unclips for a more thorough clean) resolves this without needing to replace the unit, provided the fouling hasn't been left so long that it's affected the bearing (see below).

Bearing wear — the fault that means replacement, not repair

Almost no domestic extractor fan has a user-serviceable or engineer-serviceable bearing — the motor is a sealed unit, and when the bearing wears, the whole fan is replaced rather than repaired. The characteristic symptom is a grinding or increasingly high-pitched whining noise that gets worse over a period of weeks to months, often audible even before you open the unit, and it's frequently accompanied by the noise persisting briefly for a second or two after the fan is switched off as the impeller coasts down on a rough bearing. Because bearing failure is typically a late-life symptom (fans commonly run 8–15 years before this appears), a customer reporting new grinding noise on an older fan should be quoted for a replacement fan rather than a repair — trying to nurse a failing bearing along rarely buys more than a few weeks before total seizure.

Ducting resonance — separate the duct fault from the fan fault

It's easy to misattribute a duct-borne rattle to "the fan is broken" when the fan motor itself is perfectly healthy. Trace the noise physically along the duct run from the fan body to the external grille — a rattle or buzz that changes character or intensity as you follow the duct (rather than staying constant, as a motor noise would) usually indicates a loose jubilee clip at a joint, or the duct itself vibrating against a joist, the fan housing, or another service run it's resting against. Fixes are mechanical, not electrical: re-clip and properly support the duct at appropriate intervals, and where a duct is resting against timber or another surface, wrap the contact point or reroute for clearance to stop the buzz.

External grille flap — a common false alarm

An external wall grille with a loose or worn flap can rattle in wind, particularly on an exposed elevation, entirely independently of the fan's own condition — and because it's the visible/audible part outside, homeowners often assume the fan itself is at fault. If the noise is noticeably worse in windy conditions and is present even when the fan is switched off, suspect the grille flap rather than the fan motor; replacing or resecuring the external grille (£8–£30) is a much cheaper fix than an unnecessary fan replacement.

When to replace rather than repair

As a general rule: fixing/bracket looseness, duct resonance, external grille rattle, and impeller fouling are all repairable in place without replacing the fan. Bearing wear and a damaged/unbalanced impeller are not — on the vast majority of domestic fans, these mean fitting a new unit. Any replacement fan must still meet the room's Part F ventilation rate and, where the wiring or circuit is being altered rather than a like-for-like swap, may trigger Part P notification requirements — see extractor fan not working for the full replacement compliance summary.

Frequently Asked Questions

My fan has always been slightly loud — has something actually gone wrong, or is that normal?

Some baseline running noise is normal, and boost speed on a humidistat-controlled fan is genuinely louder than trickle/background speed by design — that's not a fault. What indicates an actual developing fault is a change: new noise that wasn't there before, noise that's getting progressively worse over weeks, or a change in the character of the noise (a hum turning into a grind, for example). If the noise level and character have been stable for years, it's very likely just that fan's normal running sound.

Can I lubricate the bearing to stop the grinding noise?

No — almost all domestic extractor fan motors use sealed bearings that aren't designed to be opened, lubricated, or repacked. Attempting to do so risks damaging the motor further or introducing a safety issue. A grinding or whining bearing noise means the fan is nearing end of life; replace the unit rather than attempt a repair.

The fan is noisy but the airflow still seems fine — should I still deal with it?

Yes, treat it as worth investigating even though performance hasn't dropped yet. Loose fixings and impeller fouling both tend to develop gradually and are cheap/easy to fix while airflow is still unaffected; bearing wear specifically tends to worsen over a relatively short window (weeks to a few months) before the fan fails completely, so a new grinding noise is worth acting on promptly rather than waiting for the fan to stop working altogether.

Is the rattling noise dangerous, or just annoying?

In almost all cases it's a nuisance/reliability issue rather than a safety issue — loose fixings, duct rattle, and impeller fouling don't present an electrical or fire risk in themselves. The exception worth flagging is a fan that's vibrating enough to be working its fixings looser over time, or where wiring at the fan terminals could be disturbed by ongoing vibration — worth a visual check of the wiring connections while the cover is off for any other reason.

How do I tell if the noise is coming from the fan or the duct?

With the fan isolated and the cover off, you can distinguish by listening/feeling along the accessible duct run (where reachable) separately from the fan motor housing itself. A noise that's constant in character regardless of where you are along the duct, and loudest right at the fan body, points to the motor. A noise that changes in intensity or character as you move along the duct, or that's loudest at a specific joint or contact point, points to the ducting rather than the fan itself.

Regulations & Standards