Aircon Not Cold? We Can Fix It

Why Is Your Aircon Not Blowing Cold Air?

Few things are more uncomfortable than realising your aircon is running but not cooling, especially during Singapore’s relentless heat. You hear the unit running, feel air coming from the vents, but the room is not getting any cooler. This is one of the most common aircon complaints we receive, and the good news is that most causes are identifiable and repairable.

The key to an effective and affordable fix is proper diagnosis. Too many homeowners waste money on repeated gas top-ups or unnecessary part replacements because the root cause was never properly identified. At Cool Earth Aircon, we take a systematic approach — testing each possible cause until we find the actual problem.

Common Causes and How We Fix Them

Low Refrigerant Gas

This is the single most common reason for an aircon that is not cold. Refrigerant (commonly R410A or R22 in older units) is the medium that carries heat from your room to the outside. When levels drop, the system cannot transfer enough heat, and cooling performance drops dramatically.

Signs: Gradual loss of cooling over days or weeks, ice on copper pipes, outdoor unit running but indoor air lukewarm.

Our fix: We measure refrigerant pressure with calibrated gauges, check for leaks, repair any leak found, and top up the gas to the correct specification. A simple top-up without fixing the underlying leak is a temporary solution at best.

Dirty Evaporator Coils

Over months of operation, a thick layer of dust, grime, and biological growth coats the evaporator coil inside your indoor unit. This insulating layer prevents efficient heat exchange — the refrigerant cannot absorb heat from the air passing over the coil. The result is air that comes out only slightly cooler than room temperature.

Signs: Gradual reduction in cooling despite regular filter cleaning, musty odour from the vents, visible grime on the coil when you open the front panel.

Our fix: For moderate buildup, a chemical wash restores cooling performance. For severe cases, a chemical overhaul with full disassembly provides the most thorough cleaning.

Clogged Air Filters

The simplest and most overlooked cause. When filters are heavily clogged with dust, airflow through the evaporator coil is restricted. Less air passing over the coil means less cooling, even if every other component is working perfectly.

Signs: Weak airflow from the vents, room takes much longer to cool down, higher electricity bills.

Our fix: Filter cleaning is part of our standard servicing. If you are between service visits, you can remove and rinse your filters under running water as a temporary measure.

Faulty Thermistor Sensor

The thermistor is a temperature sensor that tells the PCB (control board) what the current room temperature is. When it malfunctions, it sends incorrect readings — the system may think the room is already cold when it is not, causing the compressor to cycle off prematurely.

Signs: Aircon starts and stops frequently, cooling works intermittently, temperature display on the unit shows incorrect readings.

Our fix: We test the thermistor with a multimeter and compare readings against specifications. Replacement is straightforward and affordable — usually completed within 30 minutes.

PCB (Control Board) Issues

The printed circuit board controls all electrical functions of your aircon — compressor operation, fan speed, temperature regulation, and error reporting. A faulty PCB can cause a wide range of symptoms, including failure to cool.

Signs: Error codes flashing on the unit, no response to remote commands, erratic behaviour, unit powers on but compressor does not start. If your unit is showing a blinking light, read our guide on what aircon blinking lights mean.

Our fix: We test PCB outputs and inputs systematically. If the board is faulty, we source a compatible replacement. For common models, we often carry replacement boards on our service vehicles.

Compressor Problems

The compressor is the heart of your aircon system. If it fails, the refrigerant cannot circulate, and there is no cooling at all. Compressor issues range from minor problems (faulty capacitor) to major failures requiring replacement.

Signs: Outdoor unit hums but does not start, unit trips the circuit breaker, no cooling whatsoever.

Our fix: We test the compressor windings, capacitor, and starter relay. Minor issues like a failed capacitor are inexpensive to fix. If the compressor itself has failed, we provide an honest assessment of whether repair or system replacement makes more financial sense.

Before You Call: Quick Checks You Can Do

Before scheduling a service call, try these simple checks that resolve the issue surprisingly often:

1. Check the remote control mode — Ensure it is set to “Cool” mode, not “Fan” or “Dry” mode
2. Set temperature to 22°C or lower — Some units will not activate cooling if the set temperature is above the current room temperature
3. Inspect air filters — Remove and check for heavy dust buildup. Rinse under water if needed
4. Check the outdoor unit — Verify it is running. If the outdoor unit is not operating, the indoor unit can only blow room-temperature air
5. Reset the circuit breaker — Turn off the aircon breaker for 30 seconds, then turn it back on

If none of these resolve the problem, it is time for professional diagnosis.

When to Consider Replacement Instead of Repair

We always give honest advice, even when it means less business for us. In some situations, repair is not cost-effective:

• The aircon is over 10 years old and uses R22 refrigerant
• The compressor has failed and is out of warranty
• Repair costs exceed 50% of a new system’s price
• The unit has required multiple repairs in the past year

A new system comes with a manufacturer warranty, better energy efficiency, and years of reliable service. We can advise on suitable replacements and provide competitive installation quotes.

Get Your Aircon Cooling Again

Do not suffer through Singapore’s heat with a malfunctioning aircon. WhatsApp Cool Earth Aircon at +65 9427 3833 and describe your problem. Our technician can often narrow down the likely cause over chat and schedule a same-day diagnostic visit.