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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.

Refrigerant is not fuel. It circulates in a sealed loop and is never consumed, so a unit that needs gas has a leak — full stop. The honest version of a regas visit: find the leak with a detector or nitrogen pressure test, repair it, pull a vacuum on the lines, then weigh in the exact charge printed on the nameplate. The dishonest version is a hose, a cylinder, and see-you-next-summer. If you have paid for top-ups two years running, you have paid twice for one unfixed leak.

The gas itself matters. Older UAE units run R22 — the gas everyone still calls freon — which is being phased out under the Montreal Protocol; imports are restricted and the shrinking supply gets pricier every year, so regassing an old R22 unit can cost a startling share of its remaining value. Most systems from the last decade use R410A, and newer machines increasingly use R32, more efficient but mildly flammable. The gases are not interchangeable: R410A runs at much higher pressures than R22, so you cannot refill an old system with new gas. When a technician says an ageing R22 unit with a leaking coil is not worth repairing, the arithmetic usually supports them.