When extraction gets noisier but weaker

It usually means grease build-up straining the fan (the noise) and choking the airflow (the weakness) - a warning that the system is grease-laden and struggling. Both symptoms point to the same cause: grease build-up. The extract fan accumulates grease (on the impeller and housing), which unbalances and loads it, so it works harder and runs louder and more strained - the noise. At the same time, grease build-up throughout the system (clogged filters, grease-laden ductwork, the loaded fan) chokes the airflow, so the system pulls less air - the weakness. So the same grease build-up strains the fan (noisier) and chokes the airflow (weaker), which is why they appear together: the system works harder against the grease resistance but achieves less airflow through the grease blockage. It means the extraction is grease-laden and straining, needing cleaning - and it is a warning to act, because the strained fan can eventually fail. So noisier but weaker means a grease-laden, straining system that needs checking and cleaning. This is general commentary.

Because grease building up on the fan unbalances and loads it, so it has to work harder and runs louder and more strained. The extract fan spins to draw the air through the system, and grease accumulates on it (the impeller/blades and housing) as the kitchen operates. This grease build-up adds weight and, crucially, unbalances the fan (the grease deposits unevenly), so the spinning fan becomes unbalanced and loaded - it vibrates, labours, and has to work harder to turn. An unbalanced, loaded fan runs louder and more strained than a clean, balanced one (rattling, humming, labouring). So the more grease builds up on the fan, the more unbalanced and loaded it becomes, and the noisier it runs. This is why extraction gets noisier as grease builds up - the fan is straining under the grease. It is also a sign of wear (a fan working harder and unbalanced is under strain that can lead to failure). So grease makes the fan noisier by unbalancing and loading it, so it strains and runs louder. This is general commentary.

Because grease build-up throughout the system chokes the airflow - clogged filters, grease-laden ductwork and the loaded fan all reduce how much air can pass through. The extraction pulls air through the system (filters, canopy, ductwork, fan), and how much it pulls depends on the path being clear. As grease builds up, it clogs and narrows that path: the grease filters clog (restricting the air entering), the ductwork accumulates grease on its internal surfaces (narrowing the duct and adding resistance), and the fan (loaded with grease) moves air less effectively. So the grease build-up chokes the airflow, restricting how much air can pass through - and the system pulls less air (weaker extraction). Even though the fan is working harder (noisier), the choked, grease-laden system lets less air through, so the actual extraction is reduced. So the extraction is pulling less air because grease build-up is choking the airflow through the system. Cleaning the system (removing the grease) restores the airflow. So it is pulling less air because grease is choking the system. This is general commentary.

It can be a warning of that - a fan straining under grease load can eventually fail (seize or burn out), so noisier-but-weaker is a sign to act before that happens. The noise indicates the fan is straining under grease build-up (unbalanced and loaded, working harder). A fan under this strain is being worn and stressed - and if the grease build-up is not addressed, the fan can eventually fail: it can seize (grease seizing the fan so it stops turning) or burn out (the motor overworked and overheated by the constant strain). A fan failure is a costly breakdown - and leaves the kitchen with no extraction (unable to operate safely). So the noisier-but-weaker warning is a sign to have the system checked and cleaned before the strained fan fails - catching the grease build-up while it is still a cleaning job, not a breakdown and fan replacement. Acting at this stage spares the fan and avoids the far greater cost and disruption of a failure. So yes - noisier-but-weaker can warn of a coming fan failure, which is why acting promptly matters. This is general commentary.

Have the system checked and cleaned - the remedy is usually cleaning the grease build-up, and acting promptly spares the fan. Since noisier-but-weaker usually means grease build-up straining the fan and choking the airflow, the response is to have the extraction checked (confirming the grease build-up in the filters, ductwork and fan) and cleaned (removing the grease throughout the system). Cleaning resolves both symptoms: the fan, cleaned and rebalanced, runs freely and quietly again; and the airflow, unchoked, is restored (effective extraction again). It also relieves the strain on the fan, sparing it from the failure it was heading toward. So act promptly - have the system cleaned before the strained fan fails (a costly breakdown). A competent extraction cleaner will clean the whole system and can confirm whether the cause is grease (usually) or something else (a mechanical fault, blockage or failing fan component, which should also be considered). So if your extraction is noisier but weaker, have it checked and cleaned promptly to restore it and spare the fan. So check and clean the system promptly. This is general commentary.

Possibly - while grease build-up is the common cause of the noisier-but-weaker combination, other causes should also be considered, so a check is worthwhile. Grease build-up is the usual cause (straining the fan and choking the airflow, producing both symptoms together), and cleaning usually resolves it. But other things can cause noise or reduced airflow, and should be considered if cleaning does not resolve it or the check suggests otherwise: a mechanical fault in the fan (a failing bearing, a loose or damaged impeller, a motor problem) causing noise; a foreign-object blockage in the system restricting airflow; a duct leak or damage reducing the effective extraction; or a failing fan losing performance. So while grease is the common and first thing to check (and clean), a competent check should also consider these other possibilities - especially if the symptoms persist after cleaning, or if there are signs of a mechanical fault (grinding, specific noises). So the noisier-but-weaker combination is usually grease, but a proper check considers other causes too. So it is usually grease, but other causes are possible and worth checking. This is general commentary.