Why Is My Aircon Not Cold Enough?
5 Common Causes

1. Dirty or Clogged Air Filter

This is the most common cause, and the easiest to check. The air filter traps dust and debris before air passes over the evaporator coil. When it gets clogged — which happens faster in Malaysia's dusty, humid conditions — airflow drops significantly. Less air over the coil means less cooling into the room.

Symptom: The unit is running, but airflow feels weak. The room cools down very slowly or not at all.

DIY fix: Most residential split units have a removable filter behind the front panel of the indoor unit. Pull it out, rinse it under running water, let it dry fully, and slot it back in. Do this every 2–4 weeks if you use your aircond daily.

Most split unit filters can be removed, rinsed, and replaced in under 10 minutes — no tools needed.

2. Low Refrigerant (Gas)

Refrigerant — commonly called "gas" — is the substance that absorbs heat from your room and releases it outside. If there's a slow leak in the system, refrigerant levels drop over time and cooling capacity drops with it.

Symptom: The unit blows air but it's not cold, even after cleaning the filter. You might also notice ice forming on the copper pipes near the indoor unit, or a hissing sound.

DIY fix: None — this requires a licensed technician. Refrigerant handling is regulated, and the leak needs to be found and sealed before topping up. Simply adding gas without fixing the leak is a temporary fix that will recur.

3. Dirty Evaporator or Condenser Coils

The evaporator coil (inside) and condenser coil (in the outdoor unit) both need to be clean to transfer heat efficiently. A layer of grime acts as insulation, reducing how much heat the coil can absorb or release.

Symptom: Cooling feels progressively weaker over months. The unit may run longer cycles than it used to without reaching your set temperature.

DIY fix: You can gently vacuum or brush the indoor unit's fins (the metal slats behind the filter), but a proper coil clean requires a technician with the right cleaning solution. This is typically done as part of a standard service or chemical wash.

4. Undersized Unit for the Room

If your aircond has always struggled to cool the room — especially when full of people, or with sunlight coming through large windows — the unit may simply be too small for the space.

Symptom: The aircond runs continuously at the lowest temperature setting but the room never gets truly cold. Problem is consistent, not recent.

DIY fix: None, but it's useful to know. Check the horsepower (HP) of your unit against the room size. A 1.0HP unit is typically adequate for rooms up to about 100 square feet. If your room is significantly larger, you may need a higher-capacity unit.

A 1.0HP unit suits rooms up to roughly 100 sq ft. Larger rooms need proportionally higher capacity.

5. Thermostat or Remote Control Issue

Sometimes the problem is not the aircon itself — it's the temperature settings or a faulty thermostat sensor.

Symptom: The unit appears to switch off before the room is properly cooled, or the set temperature on the remote doesn't match what the room actually feels like.

DIY fix: Check that the temperature sensor (a small wire probe near the indoor unit's air intake) is clean and positioned correctly. Also check that the remote's set temperature is actually lower than the current room temperature — if you've set it to 25°C and the room is 24°C, the unit won't cool further.

When to Call a Technician

If you've checked the filter and it's clean, but the unit is still not cold, the most likely culprits are low refrigerant or dirty coils — both of which need professional attention. Don't delay: running a unit with low gas strains the compressor and can lead to a much more expensive failure.