When Does Your Aircon Actually Need a Chemical Overhaul?
Routine servicing handles the surface. Chemical wash handles the coils. Chemical overhaul is what you call when those two aren't fixing it any more.
An aircon chemical overhaul is the most expensive cleaning service in the standard aircon menu. We don’t recommend it casually. Here are the five triggers that genuinely mean an overhaul (rather than a wash or routine service) is the right call. If you want a clearer picture of what the overhaul actually involves, our overhaul process walkthrough takes it step by step.
Trigger 1: Unit has been switched off for 6+ months
If your aircon has sat unused for more than half a year — common during long overseas postings, tenant turnover, or condo renovations — the inside of the fan coil has been a perfect environment for biofilm to grow undisturbed.
A wash will help but rarely fully resolves the smell that develops in those conditions. An overhaul lets us soak each component separately, which strips the buildup that has settled in places a wash can’t reach.
Trigger 2: Persistent musty smell even after a chemical wash
If you’ve had a wash done in the last 3–6 months and the smell is back, the wash addressed the visible biofilm but not the buildup inside the blower wheel or behind the drain pan. These are the spots that only an overhaul reaches.
This trigger is especially common in older units where biofilm has had years to compound.
Trigger 3: Black dust on the louvres that keeps coming back
Wiping the louvres clean and seeing black or grey dust reappear within a week means there’s a particle source inside the unit that the routine cleaning isn’t reaching. Usually it’s biofilm flaking off the back of the coil into the airflow.
A wash gives you a few extra weeks. An overhaul fixes the source.
Trigger 4: Drain pipe keeps clogging
If you’ve had the drain pipe pressure-flushed during a routine service and water dripping from the unit returns within 4–8 weeks, the source of the clog is usually inside the drain pan rather than in the pipe.
The drain pan is part of the dismantled-and-soaked component set in an overhaul. After the soak, the pan returns to clean aluminium, and the drain typically stays clear for 18+ months.
Trigger 5: Unit is 8+ years old and has never been overhauled
Even with regular routine servicing and occasional chemical washes, an aircon that has run for 8+ years in Singapore conditions accumulates biofilm in places the lighter cleaning never touches. The classic sign is a unit that “still works fine but the cooling is just not what it used to be.”
A one-time overhaul on a 8-year-old unit typically restores 15–25% of cooling efficiency that has been quietly lost over the years. It also adds 3–5 years of useful life before replacement is needed.
When an overhaul is not the right answer
Equally important — when an overhaul is the wrong call:
When the symptoms point to refrigerant or a part
If the cooling is weak but the coils are visually clean and the smell is neutral, an overhaul won’t fix it. The issue is more likely a refrigerant leak or a failing component (capacitor, blower motor, fan motor). These are repair jobs, not cleaning jobs.
When the unit is past economical repair
If the unit is 12+ years old and the compressor or fan motor is failing, an overhaul postpones the inevitable but doesn’t fix it. We’ll say so honestly and quote a replacement comparison.
When the unit is brand new
A unit less than 2 years old should not need an overhaul under normal conditions. If symptoms are appearing on a new unit, the issue is more likely an installation defect (vacuum step skipped, drain line not sloped, refrigerant undercharge) and should be investigated as a warranty claim with the installer.
How to confirm before booking
Don’t book an overhaul based on a guess. Send us a photo of the louvre and a brief description of the symptoms (and the unit’s age and last service date) on WhatsApp. We’ll tell you whether an overhaul is the right call, a wash will do, or a repair diagnosis should come first.
What an overhaul costs and how long it takes
- Cost: from S$160 per fan coil
- Time: 2–3 hours per fan coil
- Warranty: 90-day workmanship warranty
- Frequency: typically every 2–3 years once first done
For a 4-fan-coil HDB flat overhaul: roughly a full day of work, total cost in the S$640 range. We schedule overhauls one room at a time so you always have at least one cooled room during the work.
Book an overhaul
WhatsApp +65 9182 5233 with the unit count, brand, age, and the symptom you’re trying to resolve. We’ll quote the slot and the all-inclusive price before booking.