Pre-season check: the unit makes a new noise, is it from dirt?
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I switched it on for the first time this year (Panasonic 12,000 BTU, 6 years old, flat in Aviației near Herăstrău) and it has a rhythmic swishing, like a leaf caught in a fan. It sat idle all winter. It was not there last year. Do I call a repair person or a cleaning one?
What is really happening
The cross-flow roller is long and thin, spins at over 1,000 rpm and is the most contaminated component in the unit. When the biofilm dries over winter it flakes off in patches, the roller goes out of balance and air whistles through partly blocked blades. The sound is rhythmic because the same 'heavy' zone passes on every turn. A proper seasonal check includes exactly that: we listen to the noise at each fan speed, look at the roller with a torch and decide whether it is a cleaning or a repair.
- Settings and room conditions.
- Restricted airflow or dirty components.
- A technical issue requiring measurements.
Do not automatically assume low refrigerant.
- The blower (cross-flow fan) is the most fungus-contaminated component of a split unit, more than the filter or the front of the evaporator. [Indoor Air, 2023]
- Manufacturers recommend running the unit in fan-only mode for several hours to dry the interior before long periods of non-use, precisely to prevent odour and mould. [Daikin Europe, 2020]
- Washing with alkaline detergent, brushing and high-pressure rinsing reduces fungi inside the unit by more than 99%. [Indoor Air, 2023]
What we do on site
- We listen at low, medium and high speed; we check the roller and louvres with a torch.
- Sealed double cover, hose to the bucket, foil on the sofa.
- Alkaline cleaner on the roller and evaporator, contact time, adjustable pressure wash in place – we turn the roller by hand to clean every blade.
- Pan and hose, sanitising, filters, outdoor unit washed in place.
- Drying on 'Fan', then a test at all speeds. If the swish is gone, done; if not, we tell you it is the bearing and we do not take your money for a repair we do not do. See current rates on the Prices page.
What you can do yourself
- Before the first start of the season: remove the filters, look at the roller with a torch, check the outdoor unit for leaves.
- In autumn, dry the unit on 'Fan' for a few hours before leaving it off.
What NOT to do
- Do not poke sticks or a vacuum into the roller – the blades break.
- Do not call a repair service straight away for a dirty-roller noise; it costs more and does not fix it.
Prevention
Cleaning at the start of each summer, with the roller washed blade by blade, and drying on 'Fan' in autumn.
When to call us
0764 012 943, Monday–Saturday 08:00–20:00; in Aviației we can come in the evening too.
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Sources (3)
The information on this page is educational and based on cited sources; it does not replace medical advice. We do not do repairs, installation or refrigerant circuit work.