Mitsubishi Electric Aircon Chemical Wash in Punggol

Symptom one: the start-up smell

Switch the unit on after it's been off a few hours and sniff the first blast of air. Neutral: healthy — score zero. Faintly damp or dusty for a few seconds, then fine: early buildup — score one. Distinctly musty or sour, lingering minutes into operation: established biofilm on the coils and tray — score two. That smell is biological, and no amount of filter-rinsing removes it, because it lives on surfaces behind the filter.

Symptom two: water where it shouldn't be

Inspect below and around the fan coil. Bone dry, always: score zero. Occasional dampness or a dried watermark on the wall: drainage is straining under peak load — score one. Active dripping, even sometimes: the drain path is blocked and the tray is overflowing — score two. Water symptoms deserve the most urgency of the three, because the next stage is stained walls, warped furniture or a soaked mattress.

Symptom three: airflow that cleaning doesn't fix

With freshly rinsed filters and the fan on high, hold a hand to the outlet. Strong, room-filling throw: score zero. Noticeably softer than the unit's early days: score one. Weak enough that the room cools slowly despite the compressor running: the blower wheel and coil face are caked — score two. Now total it up. Zero to one: book the $40 general service and keep your money. Two to three: the $90 chemical wash is genuinely indicated. Four or more, or years without any deep clean: ask the tech to assess for the $160 overhaul — and they'll show you the coil photos before you commit to anything.

Tie-breakers for the borderline scores

Sitting at one or two and unsure which way to lean? Three tie-breakers sharpen the call. Time since any professional service: past a year of nightly use, lean wash — buildup that old is usually bonded. Runtime pattern: a unit cooling one room all night, every night, fouls two or three times faster than the same unit run a few evenings a week, so weight your score by hours, not months. And trajectory: a smell or drip that's clearly worsened over recent weeks is announcing where it's headed, whereas a faint note that's been stable for half a year can wait for a $40 service and a photographed verdict. When even the tie-breakers leave you torn, book the service — the tech's panel-open assessment settles it for $40, not $90.

Frequently asked questions