Aircon Evaporator Coil
The evaporator coil is where your aircon actually cools the air. When it is dirty or damaged, nothing downstream fixes the problem. We assess the coil's condition before recommending any service or replacement.
What This Part Does
The evaporator coil sits inside the indoor unit. Refrigerant flows through it at low pressure, making the coil surface cold. Your indoor fan blows room air across this surface. Heat transfers from the air into the refrigerant, and the cooled air is pushed back into the room.
The coil also removes humidity. As warm air passes over the cold coil surface, moisture condenses and drips into the drain pan below. In Singapore's humidity, this is a significant part of what makes the room feel comfortable.
When the coil is dirty, airflow through it is restricted. The heat transfer drops, cooling weakens, and the drain can overflow from ice melt if the coil gets cold enough to freeze.
How You Would Notice
Weak cooling that does not improve after a general service is the clearest sign of a coil problem. The filter is clean, the fan runs, but the room still does not cool the way it used to.
Ice on the indoor unit or the connecting pipe signals a blocked coil or low refrigerant. When airflow drops, the coil surface gets too cold and moisture freezes on it.
Water leaking from the indoor unit can also point to the coil — from ice melt, or a coil that is misaligned or cracked.
- Weak cooling after a recent service — airflow feels normal but room stays warm
- Ice visible on indoor unit or connecting pipe
- Water leaking from indoor unit after servicing
It Might Not Be The Coil
A dirty filter is far more common than a dirty coil and creates the same airflow restriction. We confirm filter condition before attributing anything to the coil.
A weak indoor fan motor reduces airflow across the coil without the coil being dirty. Coil cleaning in this case would not improve cooling because the fan cannot push enough air regardless.
Low refrigerant reduces the coil temperature and causes icing — same appearance as a blocked coil. Pressure testing distinguishes between the two.
How We Check
We start by confirming filter condition and fan speed. If either is compromised, we address those first. Coil assessment only makes sense after airflow is confirmed to be healthy.
We inspect the coil surface visually — looking for bio-film, mould, compacted dust, or physical damage. A coil that responds to general servicing does not need a chemical wash. One with deep-set contamination does.
We also check refrigerant pressure to rule out low gas as the cause of icing. A coil with normal pressure that is still icing has a buildup problem, not a refrigerant problem.
Physical damage — bent fins, corrosion, or a refrigerant leak at the coil — requires replacement assessment. Cleaning a damaged coil does not restore its performance.
What We Find And What Happens Next
Most coil problems are buildup — resolved by chemical wash when general servicing is not enough. Physical damage requiring replacement is less common but does occur on older units or those in harsh environments.
| Finding | Next Step |
|---|---|
| Coil dirty, no physical damage | Chemical wash, retest airflow and cooling |
| Coil icing, pressure normal | Chemical wash, confirm fin condition |
| Coil icing, pressure low | Leak test and refrigerant assessment first |
| Fin damage or corrosion | Replacement assessment |
About The Repair
Coil cleaning — chemical wash — requires partial disassembly of the indoor unit. The cleaning agent dissolves bio-film and compacted dust from inside the fin structure, which wiping cannot reach. It takes longer than a general service but is not a major job.
Coil replacement is a significant repair. The coil is a core component of the indoor unit and replacement requires sourcing a part specific to the model. On older units, the coil may no longer be available separately from the full indoor unit assembly.
If a technician recommends a chemical wash and cooling does not improve after it, the coil condition or refrigerant needs to be reassessed. A wash that does not improve performance means the cause was not buildup.
After Replacement
After a chemical wash, we run the system and confirm airflow through the coil is restored. The unit should cool noticeably better than before, and the drain should run freely without ice or overflow.
After coil replacement, we pressure-test the new coil before starting the system and recharge the refrigerant if any was lost during the job. A replaced coil with a confirmed charge should behave as a new unit.
We check the drain pan and float switch after any coil work. Coil problems often stress the drain system and those components should be confirmed clear before sign-off.
When We Tell You To Wait
If the unit cools adequately and a recent service included coil cleaning, monitoring through the next service cycle is reasonable. Buildup takes time to reach a level that affects performance.
If ice has formed on the unit, turn it off and let it defrost before running again. Running a unit with a frozen coil stresses the compressor and can cause water overflow. Contact us before restarting.
If cooling is borderline and no ice is present, schedule a service with coil inspection. We will give a clear recommendation — clean, chemical wash, or replace.