Mavis Eco Cool Aircond Service KL & Selangor
WhatsApp 019-221 7190 Call

Troubleshooting · Repair

Aircon Not Cold? 7 Causes and What They Cost to Fix

Your aircon is running, the fan is blowing, but the air coming out is warm or barely cool. Before calling a technician — or before you agree to any repair quote — it helps to know what the seven most common causes are, how each one is diagnosed, and what it realistically costs to fix in Malaysia. Some of these you can rule out yourself in five minutes. Others need a technician with a manifold gauge.

By Mavis Eco Cool · Updated 18 May 2026 · ~1,600 words

Cause 1: Dirty Filter or Coil

This is the most common cause of weak cooling in Malaysian homes, accounting for the majority of "not cold" complaints that Mavis Eco Cool technicians see. The evaporator coil — the cold-side heat exchanger inside the indoor unit — needs a clear flow of warm room air across its fins to absorb heat efficiently. When the filter is clogged or the fins themselves are coated with dust, biofilm, or mould, airflow drops and the unit loses its ability to cool the room.

How to identify: Pull out the filter. If it is visibly grey and matted, that is contributing to the problem. But even if the filter looks acceptable, the coil behind it may be clogged — visible as a dark or discoloured fin surface when you shine a torch through the filter slot.

Fix: Chemical wash — the coil needs to be flushed with a cleaning agent and water, not just brushed. Cost: RM130–RM180 per unit for wall-mount. Time: 60–90 minutes.

DIY potential: You can and should rinse the filter yourself every two to four weeks. Do not attempt to clean the coil yourself without the right tools — bending the aluminium fins worsens the airflow restriction.

Cause 2: Low Refrigerant from a Leak

The refrigerant in your aircon system is a closed loop — it should never deplete under normal circumstances. If refrigerant level is low, there is a leak somewhere in the system: at a flare fitting, a valve, or a hairline crack in the copper pipe. A low-refrigerant system loses cooling capacity gradually over weeks or months, often accompanied by ice forming on the suction line (the larger insulated copper pipe leading into the wall).

Symptoms: Gradual decline in cooling over several weeks; ice on the copper pipe; in some cases, a faint hissing sound near the indoor unit or at the outdoor unit service ports; warm air despite the compressor running.

Fix: Leak detection, repair, system vacuum, and refrigerant refill. For R32 systems (most units installed after 2015), expect RM150–RM250 total including a basic leak repair at an accessible joint. A leak in the copper pipe embedded in the wall costs more. Do not simply top up the refrigerant without locating and fixing the leak — the gas will escape again within weeks and you will be paying for the same refill repeatedly.

Important: R22 (the older refrigerant found in units predating roughly 2011) is being phased out globally. Refilling an R22 unit is possible but increasingly expensive; it is worth asking whether a unit replacement makes more economic sense.

Cause 3: Failed Compressor

The compressor is the heart of the aircon system. It compresses the refrigerant gas, raising its temperature and pressure, so that it can shed heat at the outdoor condenser. A failed compressor means no refrigerant circulation and no cooling — the fan will still blow air through the indoor unit, but it will not be cold.

Symptoms: The outdoor unit hums or clicks but the compressor does not start (you can hear the difference — a running compressor produces a steady mechanical hum; a failed one makes a click or brief hum and then goes quiet). Sometimes the breaker trips repeatedly. Total loss of cooling despite the fan working normally.

Fix: Compressor replacement costs RM800–RM1,500 for most residential split units, depending on model and tonnage. Labour is additional. For units more than eight to ten years old, it is often more economical to replace the entire system — a new inverter unit delivers significantly better energy efficiency, and the total cost of a compressor replacement plus installation on an old unit can approach the cost of a new unit.

Cause 4: Broken Capacitor

The capacitor is a cylindrical component (about the size of a large battery) inside the outdoor unit's electrical compartment. It stores and releases electrical charge to start the compressor motor and the outdoor fan motor. Capacitors fail more frequently in hot climates because heat degrades the electrolytic fluid inside them. A failed capacitor is one of the most common outdoor-unit faults in KL and Selangor.

Symptoms: The outdoor fan starts slowly or not at all. The compressor tries to start, produces a loud hum or buzz, and then trips the thermal overload. The unit may cool briefly and then shut down. In some cases the compressor runs but the fan does not, causing the outdoor unit to overheat rapidly.

Fix: Replace the capacitor. This is a straightforward repair — the technician opens the outdoor unit's electrical panel, identifies the failed capacitor with a capacitance meter, and replaces it. Cost: RM150–RM200 including parts and labour. Time: under an hour. This is one of the more cost-effective repairs — a small part that restores full system operation.

Cause 5: Fan Motor Failure

Each aircon unit has two fans: the indoor blower (which circulates room air over the evaporator coil) and the outdoor condenser fan (which blows air across the condenser coil to shed heat). Either motor can fail. Outdoor fan motor failure is more common because the outdoor unit is exposed to heat, rain, and UV degradation. When the outdoor fan fails, the condenser cannot shed heat and the system stops cooling even if the compressor is running.

Symptoms: The outdoor unit fan blades are not spinning despite the compressor running. Hot air from the outdoor unit even though it is not cooling the room. Burning or electrical smell from the outdoor unit. The circuit breaker may trip repeatedly as the motor draws excess current trying to start.

Fix: Replace the fan motor. Cost: RM200–RM350 depending on unit brand and motor specification. For indoor blower motor failure, the symptoms are no airflow from the indoor unit despite the unit appearing to run — cost is similar. Labour-wise, accessing the outdoor fan motor is straightforward; the indoor blower motor requires more disassembly.

Cause 6: Thermostat or Control Board Fault

Modern split aircon units are controlled by a PCB (printed circuit board) inside the indoor unit. The control board reads the ambient temperature sensor, controls the compressor speed (on inverter units), manages the fan speed, and communicates with the remote control receiver. A fault anywhere in this chain can cause erratic cooling behaviour, incorrect temperature sensing, or a unit that runs the fan but will not engage the compressor.

Symptoms: The unit does not respond consistently to the remote control. Error codes appear on the display (check your Daikin or Panasonic owner's manual for the specific fault code). The temperature shown on the display does not match the room temperature. The unit starts and stops cycling unusually frequently, or the compressor never engages despite the display showing cooling mode.

Fix: Diagnose the fault code first — most modern units have self-diagnostic codes that point directly at the failing component (temperature sensor, communication error, inverter board fault). Replacing a temperature sensor: RM100–RM150. Replacing the main control board: RM250–RM450 depending on brand and model. Aftermarket PCBs are available for common brands and significantly reduce cost; OEM boards from Daikin or Panasonic are more expensive but carry a warranty.

Cause 7: Undersized Unit for the Room

This one is not a fault that develops over time — it is a mismatch that existed from installation. An undersized aircon will cool the room eventually on a cool day, but during the peak of a Malaysian afternoon (outdoor temperature 34–38°C, high humidity), a 1.0 HP unit in a 250 sq ft room with west-facing windows and inadequate ceiling insulation will run continuously without ever reaching the set temperature.

Symptoms: The unit runs constantly without cycling off. The room takes an unusually long time to cool (more than 45–60 minutes to drop from 30°C to 24°C). The unit has always been this way — there is no historical baseline of better performance. TNB bills are high relative to usage because the compressor never stops.

Diagnosis: BTU calculation. A rough rule of thumb is 550–600 BTU per square foot for Malaysian conditions (adjust upward for direct sun exposure, poor insulation, or high occupant density). A 1.0 HP unit delivers approximately 9,000 BTU; a 1.5 HP unit approximately 12,000–13,500 BTU; a 2.0 HP unit approximately 18,000 BTU.

Fix: Upgrade to an appropriately sized unit, or add a second unit if the room is large or awkwardly shaped. This is a capital expense, not a repair — but continuing to run an undersized unit at full load is hard on the compressor and will result in premature failure.

How to Diagnose at Home Before Calling

Before calling a technician, run through these four checks. They take less than five minutes and will help you describe the problem accurately — or occasionally identify a simple fix you can do yourself.

  1. Check the thermostat setting. Confirm the remote is set to cooling mode (not fan-only or dry mode), the set temperature is below the current room temperature, and fan speed is set to Auto or a specific speed rather than being set to Low by accident. This sounds obvious but accounts for a surprising number of calls.
  2. Check if the indoor fan is running. Stand in front of the indoor unit. Can you feel or hear the fan blowing? If the fan is not blowing at all, the issue is in the indoor unit (blower motor, control board, or the unit is in protection mode due to a sensor fault). If the fan is blowing but the air is not cold, the problem is in the cooling circuit.
  3. Check if the outdoor unit fan is spinning. Go outside and look at the outdoor unit's top grille. The fan blades should be spinning when the unit is in cooling mode. If the fan is not spinning but the unit is making a hum, the capacitor or fan motor is likely the issue. If the outdoor unit is completely silent, the compressor is not running.
  4. Listen for the compressor click. When you turn the aircon on (or when it resumes cooling after reaching the set temperature), listen for a distinct click from the outdoor unit followed by a change in the hum as the compressor starts. No click and no change in hum after 30–60 seconds of the fan running suggests a compressor start problem (capacitor, overload, or compressor itself).

Frequently Asked Questions

How fast can you come if my aircon stops cooling?

Mavis Eco Cool offers same-day service for most jobs in KL and Selangor — WhatsApp 019-221 7190 with your location and we will confirm availability. For urgent situations (no cooling in a home with young children or elderly residents), mention this when you message and we will prioritise accordingly.

Is it worth repairing an old aircon?

A general rule of thumb: if the repair cost exceeds 50% of the cost of a new equivalent unit, replacement is usually the better economic decision — especially if the unit is more than eight years old. Older non-inverter units also use significantly more electricity than modern inverter models; the energy savings from a new unit can offset a substantial portion of the purchase cost within two to three years of daily use in Malaysia's climate.

Do you provide a quote before starting work?

Yes. Mavis Eco Cool technicians diagnose the fault first and provide a written quote before any repair work begins. You are not committed to the repair if the quote does not suit you — you pay only for the diagnostic visit in that case. For straightforward repairs (capacitor replacement, gas refill, chemical wash), we can usually provide a firm price over WhatsApp before the technician arrives.

What is the most common cause of weak cooling?

In our experience across KL and Selangor, a dirty evaporator coil (Cause 1) is the most common cause — probably 50–60% of weak-cooling calls. The second most common is low refrigerant from a slow leak (Cause 2). Both are maintenance-related rather than mechanical failures, which is why a consistent service schedule prevents the majority of "not cold" complaints before they happen.

Related Services

Sources