A few months ago I signed up for a hands-on air-conditioning servicing course at ITE Singapore, offered through the SkillsFuture programme. I went in expecting to pick up some basic DIY knowledge. I came out understanding why so many Singaporeans are quietly overpaying for a service that — with the right knowledge — costs a fraction of what companies charge.
I'm the founder of Scout, a skills marketplace built for exactly this kind of gap. This article is my honest account of what the course covered, what I learned about how your home aircon actually works, and what a "chemical wash" really costs versus what you're being billed.
How Your Home Aircon Actually Works
Most of us use our aircon every day without any idea what's happening inside the wall. The course started here — and it genuinely changed how I think about maintenance.
A standard home split-unit system has two main parts:
The indoor unit (the one mounted on your wall) contains the fan coil (also called the evaporator coil), a blower fan, an air filter, and a water tray that collects condensation. Warm air from your room is drawn over the cold fan coil, which absorbs the heat. The now-cooled air is pushed back into the room by the blower.
The outdoor unit contains the compressor — the heart of the system — along with the condenser coil and a fan. The compressor pressurises the refrigerant, releasing the heat absorbed from your room to the outside air.
Connecting the two units are refrigerant pipes (the piping structure running along your wall or ceiling) and a drain pipe that removes condensate water from the indoor unit.
The coolant — or refrigerant — is what actually moves heat between the two units. Older systems use R22, which is being phased out due to environmental concerns. Most modern home units use R410A or the newer R32, which are more environmentally friendly and energy efficient. Knowing which type your system uses matters if you ever need a top-up.
The Four Most Common Aircon Problems — Diagnosed
The hands-on portion of the course covered diagnosing the issues every Singaporean aircon owner encounters at some point.
1. Aircon not cold The most common complaint. Usually caused by one of three things: a dirty air filter or fan coil restricting airflow, low refrigerant due to a slow gas leak, or a compressor starting to fail. The first cause is 100% a maintenance issue — one you can fix yourself. The second requires a licensed technician to top up and locate the leak.
2. Water leaking from the indoor unit Almost always a blocked drain pipe or a dirty, overflowing water tray. Dust and grime accumulate in the tray over time. If the drain pipe gets clogged, the tray fills up and water spills out — often directly onto your floor or, worse, into the wall cavity. Regular cleaning prevents this entirely.
3. Smelly or musty air The blower fan and fan coil are the culprits here. Both are constantly damp from the condensation process, which makes them ideal environments for mould and bacteria to grow. The smell is the mould. The fix is cleaning — specifically, the fan coil and blower, which most standard servicing doesn't touch properly.
4. Aircon running but not cooling efficiently Often a combination of a dirty filter reducing airflow and refrigerant levels that have dropped slightly over time. Energy bills creep up before most people notice the cooling has degraded.
What You Can Actually DIY
The course covered how to safely dismantle the indoor unit cover and clean the fan coil and blower using tools that are readily available at any hardware store or on Shopee.
The basic kit: a fin coil cleaning spray (chemical cleaner), a hand pump sprayer, plastic sheeting to protect the wall, a drain bag that fits over the unit, and basic screwdrivers. Total spend: $20–35 depending on what you already own.
The process — once you've done it once — takes about 45 minutes per unit. You remove the cover, bag the unit with a drain bag, apply the coil cleaner, let it work, flush with clean water, reassemble. The chemical cleaner foams up and breaks down the dust, mould, and grease that accumulates on the fan coil. The flush carries it all into the drain bag and out through the drain pipe.
This is, functionally, what the industry calls a chemical wash.
The Chemical Wash Pricing Problem
This is the part of the course that stayed with me.
A standard chemical wash for one aircon unit in Singapore typically costs $80–$150, sometimes more depending on the company and the sales pitch. For a three-room HDB with three units, you're looking at $250–$450 in a single visit.
The actual material cost of doing the same job yourself: under $30 for supplies that cover multiple washes across multiple units. Even accounting for your time, the DIY cost is less than 20% of what most companies charge.
What some companies are billing as "chemical overhaul" or "premium chemical wash" often adds up to the same set of steps — just with a higher margin built in. The course was clear-eyed about this. The knowledge itself is not complicated. The barrier is just not knowing where to start.
What I'm Doing About It
Learning this didn't just change how I maintain my own units. It changed what I think Scout should be.
I'm now offering basic aircon servicing — cleaning, diagnostics, and minor maintenance — personally, as a provider on Scout, at a rate significantly below what established companies charge. Not because the work is worth less, but because the overhead is less, and I think skilled knowledge should be fairly priced.
If you're in Singapore and your aircon needs attention, you can find my listing on Scout. If you'd rather do it yourself, the SkillsFuture course at ITE is worth every hour.
Either way — you now know more than most people do about what's actually happening inside your wall unit, and what it actually costs to fix it.
Scout is a skills marketplace for Singapore and SEA. If you're a skilled tradesperson, list your services on Scout. If you need help at home, find a provider near you.