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Before you book anyone, work out which of three systems you live with, because the technician's scope differs completely. Villas and townhouses almost always use DX (direct expansion) systems: wall splits, or a ducted split with the air handler above a corridor ceiling and condensers on the roof. Here you own the whole refrigeration loop. Most apartment towers in Dubai Marina, Downtown, JLT, Business Bay and Al Reem use chilled water instead: a plant — the building's own, or a district cooling provider such as Empower or Tabreed — chills water centrally and pumps it to a fan coil unit (FCU) above your ceiling. There is no refrigerant in your flat at all, so nobody should ever quote you a gas top-up. What fails in an FCU is mechanical and electrical: the blower motor, the actuator valve, the thermostat, the filter and the drain pan.

The distinction matters for money as well as diagnosis. On district cooling you pay the provider for consumption and capacity, and the temperature of the water arriving at your floor is outside your technician's control. If the flat will not cool but the FCU checks out — valve opening, blower spinning, filter clean — the problem may sit at building level, which is a conversation with facilities management, not a repair bill. A good technician says this plainly instead of inventing work.

A frozen indoor coil looks like the unit is cooling too well. It is the opposite. The evaporator coil is designed to run cold but above 0°C, kept there by steady warm airflow across its fins. Restrict that airflow — a clogged filter, a dust-caked blower wheel — and the coil drops below freezing. Condensate that should drip into the pan freezes onto the fins, ice blocks more airflow, the coil gets colder still, and it snowballs until the unit blows a weak trickle of warmish air. Low refrigerant causes the same ice from the other direction: less gas means lower evaporator pressure and a colder coil. Two very different causes, two very different bills — a AED 150–300 clean, or a leak repair and regas — so a technician who quotes gas without checking the filter first is guessing at your expense.

August is peak icing season because the problems compound: humidity is at its annual maximum, filters carry three months of summer dust, and units run nearly 24 hours a day, so a marginal fault never gets a rest cycle to thaw. If you find ice, switch to fan-only mode for a few hours to melt it gently, put towels down, and do not chip at the fins — they are soft aluminium. Then book a proper diagnosis, because the ice returns within days if the cause is not found.

That musty, gym-bag smell when the AC first kicks on has a specific cause: biofilm. Fine dust that gets past the filter lands on a coil and drain pan that stay wet for six months of the year, and the mixture grows mould and bacteria. The smell is the mildest symptom — black dust streaks around supply vents and indoor allergy flare-ups point the same way, and in a country where people live sealed indoors from May to October, indoor air quality is not a luxury concern.

Duct cleaning and coil cleaning are different jobs; know which you are buying. A chemical coil wash treats the wet heart of the unit — evaporator, blower wheel, drain pan — and fixes most smells; it earns its keep annually. Duct cleaning treats the tunnels: proper firms use rotating brushes or air whips to agitate dust and a negative-pressure vacuum to extract it, section by section. A man with a household vacuum and a torch is redistributing your ducts' contents, not cleaning them. Honest frequency is boring: every two to three years, sooner after renovation (gypsum dust is ductwork's worst enemy) or when moving into a flat with unknown history. Anyone insisting every home needs it every six months is selling frequency, not hygiene.