Chemical Overhaul vs Chemical Wash: Which Does Your Aircon Need? (2026)
For most units the chemical wash (from S$90 per fan-coil) is the right deep clean: coil, blower and drain tray treated in place after partial dismantling. Book the chemical overhaul (from S$280 per fan-coil) only when a wash has already failed — smell or weak airflow that returns soon after — or when the unit has gone years without servicing and mould runs through the blower assembly.
What FixMove does
FixMove (registered ALL-IN-ONE FIX & MOVE, UEN 53505530K) comes to you anywhere in Singapore — your HDB flat, condo, office or shop. There is no counter to visit. One number covers eight kinds of work: aircon, plumbing, electrical, handyman, installation, moving, renovation and full-house customisation. We are open 24 hours, Monday to Sunday, and where the work is regulated we arrange the appropriately licensed person.
Visit charges: A S$10 fuel surcharge applies to every visit. No additional standard call-out or inspection fee applies. Urgent service or a customer-requested appointment time adds one S$30 fee, subject to technician availability and confirmation. The S$30 is a separate service fee. Repair, diagnostic labour and materials are quoted separately; work starts only after customer approval.
A S$10 fuel surcharge applies to every visit. No additional standard call-out or inspection fee applies. Urgent service or a customer-requested appointment time adds one S$30 fee, subject to technician availability and confirmation. The S$30 is a separate service fee. Pricing terms.
Both services get called "deep cleaning", both involve chemicals, and the quotes arrive side by side — one from S$90, one from S$280. The three-times price gap is not marketing: the two jobs differ in how far the fan-coil comes apart, what the chemical actually reaches, and how long the technician is on your ladder. Pick the wrong one and you either pay S$280 for a problem a S$90 wash would have solved, or pay S$90 twice before accepting that only a full strip-down will clear the mould. This guide sets out exactly what each service includes, a symptom table that points to the right treatment, the price logic, and how often each is genuinely needed in a Singapore home.
📱 WhatsApp Photos for Advice
What a chemical wash includes (from S$90 per fan-coil)
A chemical wash is the standard deep clean for a unit whose problem is dirt, not damage. The fan-coil is partially dismantled and the parts a brush cannot reach are treated in place:
- Dismantle. Front cover, filters and drain tray come off, exposing the evaporator coil and blower.
- Chemical soak of the evaporator coil. A coil-safe cleaning agent foams into the fins and dissolves the biofilm, embedded dust and mould that water and brushing cannot shift.
- Blower and drain tray cleaning. The blower wheel is treated in place and the drain tray is scrubbed or soaked — the two most common sources of the sour smell and the sludge that re-blocks drains.
- Thorough rinse. Every treated surface is rinsed so no chemical residue is left to corrode the aluminium fins.
- Drain flush, reassembly and test. The drain line is flushed, everything goes back together, and the unit is run to verify cooling and no drips.
Expect about 60-90 minutes per fan-coil unit. The key phrase is in place: the blower wheel spins on its motor shaft throughout, so the chemical reaches its outer surfaces but not the hub, the shaft or the far side of the assembly. For most units that is enough. Full pricing by unit count — including the from-S$70-per-unit rate when three or more fan-coils are done on one visit — is on the chemical wash cost page.
What a chemical overhaul includes (from S$280 per fan-coil)
A chemical overhaul is the same idea taken to completion. Instead of treating parts where they sit, the fan-coil is stripped down:
- Full disassembly. Beyond the cover and filters, the blower wheel, fan motor and drain tray are physically removed from the chassis.
- Off-unit chemical soak. The removed parts soak in cleaning solution separately, so the chemical reaches every surface — including the blower hub and the inner faces a wash never touches.
- Coil treatment with full access. With the blower out of the way, the evaporator coil is treated and rinsed from both sides rather than front-only.
- Chassis and drain path cleaning. The empty housing, drain pan seat and drain line are cleaned end to end.
- Reassembly, lubrication check and test. Parts are refitted, the fan motor's running condition is checked, and the unit is tested for cooling, noise and drips.
Plan for around 2-3 hours per unit. Refrigerant work is not part of the cleaning itself: any gas diagnosis, leak repair or refill is assessed and quoted separately, and only if needed. Per-unit rates and what affects them are on the chemical overhaul price page.
Symptom table: which treatment does your unit point to?
| Symptom | Likely treatment | Why |
|---|---|---|
| Musty or sour smell returns within days of a general service | Chemical wash | Biofilm on the coil and blower surfaces — exactly what the in-place chemical soak dissolves |
| Airflow weak although filters and cover look clean | Chemical wash | Fins clogged inside where a brush and vacuum cannot reach |
| Water drips again soon after a drain flush | Chemical wash | Sludge in the drain tray keeps re-seeding the blockage; the tray needs a chemical scrub, not just a flush — flush-only is from S$60 when a blocked accessible drain line is the confirmed cause |
| Smell or weak airflow comes back soon after a chemical wash | Chemical overhaul | Build-up sits inside the blower hub or behind the coil, where only full removal and soaking reaches |
| Black mould visible through the whole blower assembly, or unit unserviced for years | Chemical overhaul | Contamination is past what in-place treatment can clear; the parts need to come out |
| Air not cold at all, or cooling lost suddenly | Neither — diagnose first | Points to low refrigerant (a gas top-up runs S$80-150 for R32), an electrical fault or a compressor issue; see the aircon-not-cold page before approving any deep clean |
The pattern to remember: a wash treats surfaces, an overhaul treats the whole assembly. If the problem survives a properly done wash, more washing will not fix it — and if the unit has never had a wash, jumping straight to an overhaul is usually paying for depth you do not need yet.
The price logic: why the overhaul costs about three times more
FixMove's published figures, in one place:
| Service | Price | Time per unit |
|---|---|---|
| General servicing | From S$50 | ~30-45 min |
| Chemical wash (fan-coil) | From S$90 · from S$70/unit for 3+ units on one visit | 60-90 min |
| Chemical overhaul | From S$280 | 2-3 hours |
| Outdoor unit wash | From S$80 | Access-dependent |
| Drainage pipe flush only | From S$60 | Where a blocked accessible drain line is the confirmed cause |
The gap between S$90 and S$280 is mostly labour and risk. An overhaul roughly doubles or triples the time on site, involves removing and refitting the fan motor and blower wheel (the step where an inexperienced hand causes damage), and cleans parts off-unit where they can be soaked properly. That is also why the overhaul is not "a better wash you should always choose" — on a unit whose fouling is surface-level, the extra depth changes nothing you can feel. Full breakdowns are on the chemical wash cost page and the chemical overhaul price page; exact figures for your unit count, model and access are confirmed in a written WhatsApp quote before any work.
How often is each needed?
- General service: every 3-4 months. The baseline that keeps both deep cleans further apart — schedule details are in our guide on how often to service your aircon.
- Chemical wash: every 12-18 months for a typical HDB unit, symptom-led. A lightly used, well-maintained bedroom unit can stretch longer; book on symptoms, not the calendar.
- Chemical overhaul: no fixed schedule at all. It is an escalation, not a routine — book one when a wash has failed or the unit has gone years unserviced. A unit kept on the two intervals above may never need one.
Be wary of any package that puts an overhaul on an annual schedule by default. The overhaul exists to rescue units that maintenance has already failed; putting it on a calendar for a maintained unit reverses the logic and roughly triples your deep-cleaning spend for no felt difference.
Aftercare: making either service last
What you do in the weeks after a wash or overhaul decides how soon you pay for the next one:
- First 48 hours: watch for drips. The drain path was disturbed during reassembly; a drip in the first two days is a workmanship issue, not a new fault — report it under the written warranty rather than living with it.
- The smell test is immediate. A correct wash or overhaul removes the musty smell from day one. If it creeps back within a couple of weeks, part of the build-up was missed — go back to the company with that symptom in writing.
- Wash the filters yourself monthly. Ten minutes at the sink is the single cheapest way to slow re-fouling of the coil you just paid to clean.
- Restart the 3-4 month general service cycle. Especially after an overhaul: the unit is internally close to clean-as-installed, so treat the overhaul date as day zero of a fresh maintenance schedule instead of waiting for symptoms to rebuild.
- Keep the setpoint sensible. NEA's recommended 25°C reduces condensation load on the freshly cleaned coil and tray — and your bill.
📱 WhatsApp +65 9823 7108 📞 Call +65 9823 7108
Related reading
- Aircon Chemical Wash Cost Singapore — full price breakdown, from S$90
- Aircon Chemical Overhaul Price Singapore — per-unit rates, from S$280
- Chemical Wash vs General Servicing — the step below this comparison
- How Often Should You Service Your Aircon in Singapore?
- Aircon Not Cold — Diagnosis First
- Aircon Servicing Singapore — all services, from S$50
- All FixMove guides
FAQ
What is the difference between a chemical overhaul and a chemical wash?
A chemical wash partially dismantles the fan-coil and treats the evaporator coil, blower and drain tray in place with a coil-safe cleaning agent — from S$90 per unit, taking about 60-90 minutes. A chemical overhaul strips the fan-coil completely, with the motor, blower wheel and drain tray removed and soaked separately — from S$280 per unit, taking around 2-3 hours. The overhaul reaches build-up inside the blower assembly and behind the coil that a wash cannot.
Is an aircon chemical overhaul worth it?
It is worth it when a standard chemical wash no longer fixes the problem: a smell or weak airflow that returns soon after a wash, mould through the whole blower assembly, or a unit that has skipped servicing for years. On a unit maintained every 3-4 months it is rarely justified — a from-S$90 chemical wash usually restores performance at roughly a third of the overhaul price. On a very old unit, compare the overhaul quote against replacement before committing.
How often should a chemical overhaul be done?
There is no fixed schedule. An overhaul is symptom-led: book one only when a chemical wash fails to clear the smell, airflow or drainage problem, or when a unit has gone years without any servicing. Many units that get a general service every 3-4 months and a chemical wash every 12-18 months never need an overhaul at all.
Can a chemical overhaul fix an aircon that is not cold?
Only when heavy internal fouling is the confirmed cause. Sudden or total loss of cooling more often points to low refrigerant — a gas top-up runs S$80-150 for R32 — or an electrical or compressor fault, none of which cleaning fixes. Work through the aircon-not-cold page and get the actual cause diagnosed before approving an overhaul quoted as a cooling fix; refrigerant diagnosis and any refill are scoped and quoted separately.
Published: 16 July 2026 · Updated: 16 July 2026 · By FixMove Home Repair Team. References: NEA (25°C setpoint guidance), Meteorological Service Singapore (humidity data).