It is the hottest part of the afternoon in Petaling Jaya, and your aircond is running but the room is still warm. You turn the temperature down to 16 degrees, switch to high fan speed, and wait. Nothing changes. The air coming out of the unit is barely cool, or worse, it feels like room temperature.
This is one of the most common aircond complaints we receive, and the good news is that most causes are fixable without replacing the entire unit. Here are the seven most common reasons your aircond is not cold and what you can do about each one.
1. Dirty Air Filters
The most common cause, and the easiest to fix.
Your aircond filters are the first line of defence against dust, pet hair, and airborne particles. When these filters become clogged, they restrict airflow over the evaporator coil. Less airflow means less cooling, even though the compressor is working at full capacity.
How to check: Pull out the front panel of your indoor unit and slide out the filters. If they look grey, dusty, or you cannot see through them when held up to light, they need cleaning.
The fix: Rinse the filters under running water, let them dry completely, and slide them back in. This takes 10 minutes and costs nothing. You should be cleaning your filters every 2 to 4 weeks in Malaysia.
Impact: Dirty filters can reduce cooling efficiency by 15 to 30 percent. Simply cleaning them often solves the “not cold” problem immediately.
2. Dirty Evaporator Coil
Even with clean filters, fine dust particles eventually pass through and accumulate on the evaporator coil over months and years. This layer of grime acts as insulation, preventing the refrigerant inside the coil from absorbing heat from the room air efficiently.
How to check: Remove the filters and look at the metal fins behind them. If they appear dark, coated with a film, or have visible mould growth, the coil needs cleaning.
The fix: A standard cleaning can remove surface dust, but if the buildup is significant, you will need a chemical wash. The chemical solution dissolves deep-seated grime that water alone cannot remove.
Impact: A dirty evaporator coil can reduce cooling capacity by 20 to 40 percent and significantly increase electricity consumption.
3. Low Refrigerant (Gas) Level
Refrigerant, commonly called “gas” in Malaysia, is the substance that actually absorbs heat from your room and releases it outside. If the refrigerant level drops below the required amount, your aircond cannot cool effectively.
How to check: Signs of low refrigerant include:
- The aircond blows slightly cool air but cannot reach the set temperature
- Ice formation on the copper pipes or evaporator coil
- The compressor runs continuously without cycling off
- A hissing sound near the indoor or outdoor unit
The fix: Refrigerant does not get “used up” during normal operation. If the level is low, it means there is a leak somewhere in the system. A technician needs to locate and repair the leak, then recharge the system with the correct amount of refrigerant.
Important warning: Some dishonest technicians will simply top up the gas without fixing the leak, which means you will have the same problem again in a few months. Always insist on a leak test before any gas top-up. We will cover this topic in more detail in our article about common aircond scams.
Cost: Gas top-up typically costs RM100 to RM200. If a leak repair is needed, expect RM200 to RM500 depending on the location and severity of the leak.
4. Faulty or Dirty Compressor
The compressor is the heart of your aircond system. Located in the outdoor unit, it pressurises the refrigerant and circulates it through the system. If the compressor is not functioning properly, cooling will be weak or nonexistent.
How to check: Go outside and listen to the outdoor unit. Is it running? Is it making unusual noises (clicking, grinding, or buzzing)? If the outdoor unit is completely silent while the indoor unit is running, the compressor may have failed or a related component like the capacitor may be faulty.
The fix: Compressor issues require professional diagnosis. The problem could be a failed capacitor (cheap fix, RM80 to RM150), a burnt winding (expensive, may require compressor replacement), or simply a dirty condenser coil restricting heat dissipation.
Impact: A compressor replacement on a residential unit costs RM800 to RM2,000, which is why regular maintenance to prevent compressor stress is so important.
5. Undersized Unit for the Room
This is a design problem rather than a fault. If your aircond is too small for the room it is trying to cool, it will run continuously without ever reaching the desired temperature.
How to check: As a rough guide for Malaysian conditions:
| Room Size | Recommended HP |
|---|---|
| Small bedroom (100-150 sq ft) | 1.0 HP |
| Medium bedroom (150-250 sq ft) | 1.5 HP |
| Living room (250-400 sq ft) | 2.0 HP |
| Large living room (400-600 sq ft) | 2.5-3.0 HP |
These recommendations assume standard ceiling height (about 9 feet) and moderate heat load. Rooms with large windows facing the sun, rooms on the top floor, or rooms with many heat-generating appliances may need a higher capacity unit.
The fix: Unfortunately, there is no quick fix for an undersized unit. You either need to upgrade to a higher horsepower unit or supplement with an additional unit. However, before jumping to this conclusion, make sure the existing unit is clean and properly maintained. A well-maintained 1.5 HP unit will cool better than a dirty 2.0 HP unit.
6. Blocked or Restricted Airflow
Even with a perfectly functioning aircond, blocked airflow can make it seem like the unit is not cooling. Common airflow restrictions include:
- Furniture placed directly in front of the unit, blocking the cold air from circulating
- Curtains draped over or near the outlet, redirecting the airflow upward
- Closed doors in the room preventing air circulation in connected spaces
- A faulty blower fan motor running at reduced speed
The fix: Rearrange furniture to ensure at least 1 metre of clearance in front of the indoor unit. Make sure curtains do not obstruct the airflow. If the blower fan speed seems slower than usual, this could indicate a failing motor or a heavily soiled blower fan that needs chemical wash cleaning.
7. Thermostat or Sensor Problems
Modern aircond units use a temperature sensor (thermistor) mounted near the evaporator coil to measure room temperature. If this sensor is displaced, damaged, or giving incorrect readings, the aircond may shut off the compressor prematurely, thinking the room has already reached the set temperature.
How to check: If your aircond cools well for a few minutes, then the compressor stops (the outdoor unit goes quiet) even though the room is still warm, a sensor issue is likely.
The fix: Sometimes the sensor wire has simply been knocked out of position during a previous cleaning. A technician can reposition it in seconds. If the sensor itself is faulty, replacement is inexpensive (RM50 to RM100 including labour).
Quick Troubleshooting Checklist
Before calling a technician, try these steps:
- Clean or replace the air filters - This solves the problem 30% of the time
- Check the remote control settings - Make sure you are in cooling mode (not fan-only or dry mode) and the temperature is set low enough
- Check the outdoor unit - Is it running? Is it obstructed by objects or vegetation?
- Verify the circuit breaker - Sometimes the outdoor unit circuit trips while the indoor unit keeps running
- Wait 3 minutes - If you turned the aircond off and back on, most units have a 3-minute compressor protection delay
When to Call a Professional
If you have cleaned the filters, verified the settings, and the aircond still is not cold, it is time to call a technician. Do not attempt to open the refrigerant system, disassemble the outdoor unit, or work on electrical components yourself. These tasks require proper tools, training, and refrigerant handling certification.
At PJ Kool Aircond Service, our technicians carry diagnostic equipment that can quickly identify whether the issue is a dirty coil, low refrigerant, a faulty component, or something else entirely. Most “not cold” problems can be resolved in a single visit, and we always explain the issue and the cost before proceeding with any repair.
The key takeaway is this: an aircond that is not cold is not necessarily broken. In most cases, it just needs proper cleaning and maintenance. Regular servicing every 3 months prevents the majority of cooling problems and keeps your electricity bills under control.
If your aircond is still not cooling after cleaning, it may need a professional repair. Our aircond repair and diagnostics service includes a full inspection for RM 50 — waived if you proceed with the repair.
