Why Is My Aircond Not Cooling? 7 Common Causes

Living in Kuala Lumpur means your air conditioner is a survival tool, not a luxury. We receive hundreds of calls every month from homeowners in Kepong and the Klang Valley facing the exact same struggle: the unit is running, but the room remains uncomfortably warm.

You might be surprised to learn that many of these issues are preventable or easily diagnosable. Based on our experience servicing thousands of residential units across Malaysia, we have identified the specific culprits that plague our tropical, high-humidity climate.

Here is a breakdown of the 7 most common reasons your aircond isn’t cooling properly and exactly what you need to do about them.

1. Dirty or Clogged Air Filter

The most common cause of poor cooling is a dirty air filter. In our urban environment, construction dust and seasonal haze accumulate on filters much faster than manufacturers’ standard estimates suggest.

Why this matters:

When the filter is clogged, airflow is restricted, and your unit has to work significantly harder. The U.S. Department of Energy reports that replacing a dirty filter with a clean one can lower your air conditioner’s energy consumption by 5% to 15%. That is a direct saving on your monthly Tenaga Nasional Berhad (TNB) bill.

How to check:

• Open the front panel of your indoor unit.
• Remove the filter(s).
• Hold it up to a light source. If you cannot see light through the mesh, it is blocking airflow.

Solution:

• Clean filters every 2 weeks during heavy usage periods.
• Rinse with water and let them dry completely before reinstalling.
• This is a 100% DIY-friendly task that requires no tools.

2. Low Refrigerant Gas (And the R22 Phase-Out)

If your aircond is low on refrigerant gas, it cannot transfer heat effectively. We often have to explain that gas does not get “used up” like petrol in a car. If it is low, you almost certainly have a leak in the copper piping.

The “Old Unit” Warning:

If your unit is more than 10-12 years old, it likely uses R22 gas. Malaysia is currently in Stage III of the HCFC Phase-out Management Plan (HPMP), which strictly limits the import of R22. Servicing these older units is becoming increasingly expensive, and parts are harder to find.

Signs of low gas:

• Aircond runs but the air feels room temperature.
• Ice forms on the copper pipes near the outdoor unit.
• Hissing sounds coming from the indoor unit.

Solution:

• This requires professional service to locate and braze the leak.
• Pro Tip: Never pay for a “top-up” without fixing the leak first, or you will be paying again in two months.
• Our chemical wash includes a gas pressure check to ensure your system is sealed.

3. Dirty Evaporator Coils (The “Bio-Slime” Problem)

Even if your filters are clean, the internal evaporator coils can accumulate a layer of grime over time. In Malaysia’s high humidity (often exceeding 80%), this dust mixes with moisture to create a “bio-slime” or jelly-like substance that coats the coils.

The impact on efficiency:

A study by the EPA indicates that as little as 0.042 inches (about 1mm) of dirt on a cooling coil can reduce efficiency by 21%. This forces your compressor to run longer to achieve the same temperature.

Signs:

• Gradual decrease in cooling power over 6-12 months.
• A musty or sour smell when the aircond first starts.
• Water leaking from the front of the unit (caused by slime blocking the drainage).

Solution:

• General Service: Good for minor dust.
• Chemical Wash: Required for “bio-slime.” This restores up to 95% of original cooling capacity.
• We generally recommend a chemical wash once a year for units used daily.

4. Blocked Condenser (Outdoor Unit)

The outdoor unit (compressor) releases the heat absorbed from your room. If this unit cannot “breathe,” the heat remains trapped in the system, and your room stays hot.

High-Rise Challenges:

We often see this in condos where the outdoor unit is placed in a small balcony or “air well” with poor ventilation. If you stack boxes, dry clothes, or place potted plants directly in front of the fan, you are killing the unit’s efficiency.

Common issues:

• Debris (leaves, trash) blocking airflow.
• Dirt buildup on condenser fins.
• Unit placed in an enclosed space without adequate heat dissipation.

Solution:

• Keep at least 1-2 feet of clearance around the outdoor unit.
• Clean visible debris from the fan grille.
• If the fins are black with dirt, professional chemical cleaning is needed.

5. Faulty Compressor (Or Just a Bad Capacitor?)

The compressor is the “heart” of your aircond, but there is a smaller, cheaper part that often mimics a heart attack: the Capacitor.

The Capacitor Secret:

The capacitor is like a battery that gives the compressor the jolt it needs to start. In our hot tropical climate, capacitors tend to fail every 3-5 years due to heat stress. Many homeowners panic thinking they need a new compressor (RM1,000+), when they only need a new capacitor (RM150-RM250).

Signs of failure:

• The outdoor unit hums or buzzes but the fan doesn’t spin.
• The circuit breaker trips immediately when the compressor tries to kick in.
• The unit blows warm air despite the indoor fan running.

Symptom	Likely Culprit	Estimated Repair Cost
Loud mechanical banging	Broken Compressor	High (May need new unit)
Humming / buzzing sound	Failed Capacitor	Low (Simple part swap)
Fan not spinning	Fan Motor or Capacitor	Medium

Solution:

• Professional diagnosis is essential to distinguish between a dead compressor and a bad capacitor.
• If the compressor itself is dead and the unit is over 8 years old, we usually recommend replacing the entire unit rather than repairing it.

6. Electrical or Board Issues

Sometimes the hardware is fine, but the “brain” of the aircond is confused. In areas like Kepong, power fluctuations from thunderstorms can occasionally damage sensitive electronic boards (PCBs).

Signs:

• Aircond cycles on and off rapidly (short-cycling).
• The temperature display shows error codes.
• Remote control commands are ignored or delayed.

Solution:

• Check the batteries in your remote control first (it happens more often than you think).
• Reset the unit by turning off the main power switch (isolator) for 5 minutes, then turning it back on.
• If issues persist, we offer an RM50 diagnostic service (waived with repair) to test the PCB sensors.

7. Undersized Unit

If your aircond never cooled the room properly from day one, it might simply be too small for the space. Standard sizing guides often underestimate the cooling load needed for Malaysian homes, especially for rooms facing the afternoon sun.

Tropical Sizing Guide:

This chart adjusts for our local climate and typical concrete construction heat retention.

Room Size	Recommended Horsepower (HP)	Best For
Up to 150 sq ft	1.0 HP	Small Bedroom
150 - 220 sq ft	1.5 HP	Master Bedroom
220 - 350 sq ft	2.0 HP	Living / Dining Room
350 - 450 sq ft	2.5 HP	Large Open Plan Area

Other factors:

• Ceiling Height: If your ceiling is above 10 feet (common in older terrace houses), add 10% to the required capacity.
• Sun Exposure: West-facing windows require significantly more cooling power.

Solution:

• Upgrade to a higher capacity unit.
• Install heavy curtains or window tinting to reduce heat load.

Quick Troubleshooting Checklist

Before calling a technician, try these simple steps to rule out basic errors:

1. ✅ Clean the air filter (This fixes 30% of calls we receive).
2. ✅ Check the outdoor unit to ensure it isn’t covered by clothes or debris.
3. ✅ Verify the remote settings are on “Cool” mode (snowflake icon), not “Fan” or “Dry.”
4. ✅ Reset the breaker by flipping the main switch off and on again.
5. ✅ Close all doors and windows to ensure no cool air is escaping.

If you have checked all these boxes and the room is still warm, you likely have a refrigerant leak or a component failure that requires professional aircond repair.

When to Call a Technician

You should contact a professional if:

• Basic troubleshooting improves nothing.
• You see ice forming on the pipes or unit.
• The outdoor unit is making loud, unusual noises.
• You suspect an electrical burning smell.

Our team specializes in diagnosing these specific local issues. WhatsApp us to schedule a service call today.