Aircon Not Cold? Common Causes & How We Fix It

Aircon Not Cold? Here Are the Most Common Causes

Your aircon is running, the remote shows 16°C, but the room is still warm. This is one of the most common aircon complaints in Singapore - and the good news is, most cases have a straightforward fix.

At Billy Aircon, our technicians follow a systematic diagnostic process to identify the root cause quickly and accurately. Here are the most common reasons your aircon is not cold, ranked from simplest to most complex.

Common Causes (and Their Fixes)

1. Dirty Air Filter

The most common cause. A clogged filter blocks airflow over the evaporator coil, dramatically reducing cooling performance. You might notice the aircon blowing air, but it is not cold.

Fix: Remove and wash the filter, or have it cleaned during a regular servicing. This takes minutes and costs almost nothing.

2. Low Refrigerant Gas

If your aircon gradually loses cooling over weeks or months, low gas is likely the cause. The unit may also form ice on the evaporator coil.

Fix: Gas top-up with the correct refrigerant type. We also check for leaks to prevent the problem from recurring.

3. Dirty Evaporator Coil

Even with regular aircon servicing, grime can build up on the evaporator coil over time - especially in Singapore’s humid environment. A dirty coil cannot absorb heat efficiently.

Fix: A chemical wash dissolves the built-up grime and restores full cooling performance.

4. Faulty Compressor

The compressor is the heart of your aircon system. If it fails, the unit will blow air but produce no cooling at all. You might hear the unit running but notice zero temperature change.

Fix: Compressor repair or replacement. If the unit is old, replacement of the entire system may be more cost-effective.

5. Defective Capacitor

The capacitor provides the electrical boost needed to start the compressor. A failing capacitor causes the compressor to struggle or not start at all.

Fix: Capacitor replacement - a relatively affordable repair.

6. Faulty Thermistor or PCB Board

The thermistor (temperature sensor) tells the PCB board when to activate cooling. If either component malfunctions, the aircon may not cool to the set temperature or may cycle on and off erratically.

Fix: Sensor or PCB replacement after diagnostic testing.

Our Diagnostic Process

When you call us for an aircon not cold issue, our technician follows this process:

1. Check the basics - Filter condition, remote control settings, circuit breaker.
2. Measure temperatures - Inlet and outlet air temperature to quantify the cooling deficit.
3. Check gas pressure - Connect gauge manifold to measure refrigerant levels.
4. Inspect the coils - Check evaporator and condenser coils for dirt and blockage.
5. Test electrical components - Compressor, capacitor, thermistor, and PCB board.
6. Provide diagnosis - Explain the cause and recommended fix with transparent pricing.

We always get your approval before starting any repair.

Quick Troubleshooting Checklist (Before Calling Us)

Before scheduling a service call, try these simple checks:

Check	What to Do
Remote settings	Ensure mode is set to “Cool” (not “Fan” or “Dry”) and temperature is below room temperature
Filter	Remove and inspect - if visibly dirty, wash with water and let dry
Circuit breaker	Check if the aircon circuit breaker has tripped
Airflow	Ensure furniture or curtains are not blocking the air outlet
Outdoor unit	Check that the outdoor condenser is not blocked by debris

If these checks do not solve the problem, the issue is likely internal and requires a professional diagnosis.

When to Repair vs Replace

Factor	Consider Repair	Consider Replacement
Age of unit	Under 8 years	Over 10 years
Repair cost	Under 50% of new unit	Over 50% of new unit
Frequency	First time issue	Recurring problems
Refrigerant	R410A or R32	R22 (being phased out)
Energy bills	Normal	Noticeably high

Our technicians will always give you an honest assessment. If repair does not make financial sense, we will tell you.

Get Your Aircon Cooling Again

Do not suffer through Singapore’s heat with a malfunctioning aircon. WhatsApp us now or call +65 9456 0875 for same-day diagnosis and repair. Our team serves all areas of Singapore.