Why Is Your Aircon Not Cold?
Few things are more frustrating in Singapore than coming home after a long day to find your aircon blowing lukewarm air. With outdoor temperatures frequently above 32°C and humidity making it feel even hotter, a working aircon is not a comfort — it is essential for quality of life, proper sleep, and even the wellbeing of your electronics and furniture.
The good news is that most causes of an aircon not cooling properly are fixable, often quickly and affordably. The key is diagnosing the root cause correctly so that the right fix is applied the first time. At Billy Aircon, a leading aircon servicing company in Singapore, our technicians systematically check every possible cause, starting from the simplest and most common issues before moving to more complex ones.
Here are the most common reasons your aircon is not blowing cold air, what you can check yourself before calling a professional, and how we fix each issue.
Common Cause 1: Dirty Air Filters
This is the single most common reason an aircon stops cooling effectively, and it is also the easiest to fix. Your aircon’s air filters trap dust, pet hair, and airborne particles to keep the air clean. Over time, especially in Singapore where construction dust and urban pollution are constant, these filters become clogged.
When filters are heavily clogged, airflow through the evaporator coil is restricted. The coil cannot absorb enough heat from the room, so the air coming out feels lukewarm instead of cold. In severe cases, restricted airflow can cause the evaporator coil to freeze over with ice, which blocks cooling entirely.
DIY check: Open the front panel of your indoor unit and pull out the filters. If they are visibly grey or brown with dust, this is likely contributing to your cooling problem. You can wash them with running water and a soft brush, let them dry completely, and reinstall them. If cooling improves, your filters were the issue.
Our fix: During regular servicing, we clean the filters thoroughly with antibacterial solution. For units with severely dirty coils behind the filters, a chemical wash may be needed to restore full cooling performance.
Prevention: Clean or have your filters serviced every 3 to 4 months. Set a reminder on your phone. This single habit prevents the majority of aircon cooling problems.
Common Cause 2: Low Refrigerant Gas
Refrigerant is the substance your aircon uses to absorb heat from indoor air. If refrigerant levels drop due to a leak in the system, your aircon cannot absorb enough heat, resulting in warm or insufficiently cold air.
Signs of low gas:
- Aircon runs but air feels lukewarm, not cold
- The aircon runs continuously without cycling off
- Ice forms on the copper pipes or evaporator coil
- You hear hissing or bubbling sounds from the unit
- Electricity bill has increased noticeably
Our fix: We measure refrigerant pressure with professional gauges, check for leaks using electronic leak detectors, repair any leaks found, and perform a gas top up to restore the correct refrigerant charge. R22 systems cost $50 to $80, R410A systems $60 to $150, and R32 systems $80 to $200 for the top up, depending on how much gas is needed.
Important: Simply topping up gas without fixing the leak is a waste of money. The gas will leak out again within weeks to months. We always check for leaks first and recommend repair before topping up.
Common Cause 3: Dirty Evaporator Coil
Even with regular filter cleaning, fine dust particles gradually accumulate on the evaporator coil surface. Over 6 to 12 months, this buildup forms an insulating layer that prevents efficient heat exchange. The coil cannot absorb heat properly, so your aircon blows air that is not as cold as it should be.
Signs of a dirty coil:
- Gradual decline in cooling performance over months
- Aircon used to be cold but has slowly become less effective
- Standard servicing provides only temporary improvement
- No issues with gas levels (confirmed by pressure test)
Our fix: A non-dismantle chemical wash ($80 to $100 per unit) or full chemical overhaul ($130 to $180 per unit) dissolves the grime layer on the coil and restores efficient heat exchange. Most customers notice an immediate and significant improvement in cooling after a chemical wash.
Common Cause 4: Faulty Compressor
The compressor is the heart of your aircon system. Located in the outdoor condenser unit, it compresses the refrigerant gas and pumps it through the system. When the compressor fails or weakens, the refrigerant cannot circulate properly, and cooling stops.
Signs of compressor problems:
- The outdoor unit is not running or makes clicking sounds but does not start
- The outdoor unit runs but the indoor unit blows room-temperature air
- Unusual loud noises from the outdoor unit
- The circuit breaker for the aircon trips repeatedly
Our fix: We test the compressor’s electrical characteristics including resistance, current draw, and start capacitor. If the compressor has failed, replacement is possible but expensive — typically $400 to $1,200 depending on the unit capacity and brand. For older units beyond 8 years, we may recommend replacing the entire system rather than investing in a compressor replacement.
Important note: Compressor failure is often the result of long-term neglect. Regular servicing keeps the system clean and running smoothly, which significantly extends compressor life. A compressor that is constantly overworked due to dirty coils, restricted airflow, or low gas wears out much faster.
Common Cause 5: Faulty PCB (Printed Circuit Board)
The PCB is the electronic brain of your aircon, controlling the compressor, fan motors, temperature sensors, and all system functions. When the PCB malfunctions, it can cause a range of symptoms including failure to cool.
Signs of PCB problems:
- Aircon turns on but does not respond to temperature settings
- Unit displays error codes on the panel or remote
- Random shutdowns or restarts
- Fan runs but compressor does not activate
- Lights on the indoor unit blink in unusual patterns
Our fix: We diagnose PCB issues using the unit’s error code system and electrical testing. If the PCB is faulty, we can replace it with an original or compatible board. PCB replacement typically costs $150 to $400 depending on the brand and model. We always check if the PCB failure was caused by an underlying electrical issue (like voltage surges) to prevent recurrence.
Common Cause 6: Faulty Thermistor (Temperature Sensor)
The thermistor is a small temperature sensor that tells the aircon’s PCB what the current room temperature is. Based on this reading, the system decides how much cooling is needed and when to cycle the compressor on and off. If the thermistor gives incorrect readings, the aircon may think the room is already cold and reduce or stop cooling.
Signs of thermistor problems:
- Aircon cools intermittently — sometimes cold, sometimes not
- The unit cycles on and off too frequently or too infrequently
- Room temperature does not match the set temperature
- Aircon overcools or undercools consistently
Our fix: We test the thermistor’s resistance at known temperatures to verify accuracy. A faulty thermistor is a relatively inexpensive fix — the part itself costs $20 to $50, and installation takes about 30 minutes. Despite being a minor component, a faulty thermistor can make your entire aircon seem broken.
Common Cause 7: Blocked or Restricted Airflow
Even if all internal components are working perfectly, your aircon cannot cool effectively if airflow is restricted. This can happen due to external factors that homeowners often overlook.
Common airflow restrictions:
- Furniture, curtains, or shelves placed directly in front of the indoor unit, blocking air intake or output
- The indoor unit’s front panel is not properly closed after filter cleaning
- The outdoor condenser is obstructed by plants, boxes, or debris, preventing heat dissipation
- Room is too large or too poorly insulated for the unit’s BTU capacity
DIY check: Make sure nothing is blocking the indoor unit’s intake (top) or output (bottom). Check that the outdoor condenser has at least 30cm of clear space on all sides. Remove any objects stored near the condenser. If your room has large windows with direct afternoon sun exposure, the heat gain may exceed the unit’s cooling capacity.
Our fix: We assess the unit’s capacity relative to the room size and heat load. If the unit is undersized, we recommend upgrading to a higher capacity model or improving insulation (blinds, curtains, window film) to reduce heat gain. For obstructed condensers, simply clearing the area often makes a noticeable improvement.
DIY Checks Before Calling a Professional
Before you call us, there are a few simple things you can check yourself. These take only a few minutes and may resolve the issue without a service call:
Check the remote control settings — Make sure the mode is set to “Cool” (not “Fan” or “Dry”), the temperature is set to 24°C or lower, and the fan speed is on “Auto” or “High”. It sounds obvious, but accidental setting changes are more common than you might think, especially in households with children.
Check the air filters — Open the front panel, remove the filters, and wash them if dirty. Reinstall once dry and test. This alone fixes a surprising number of “aircon not cold” complaints.
Check the outdoor unit — Go outside and confirm the outdoor condenser is running. If it is not running at all, check whether the circuit breaker has tripped. If the condenser is running but the fan is not spinning, turn off the aircon and call a professional.
Check for ice — If you see ice on the copper pipes or on the evaporator coil behind the filters, turn off the aircon and let it defrost for 2 to 3 hours. Once melted, turn it back on. If ice forms again, call us — you likely have a refrigerant issue.
Check the timer — Some aircon units have a timer that may have been set accidentally. Check that no timer is active on the remote control.
If none of these checks resolve the issue, it is time to call a professional. Continuing to run an aircon with a known problem — especially one that involves ice formation or the outdoor unit not running — can cause further damage.
When to Call a Professional
Call Billy Aircon immediately if:
- Your aircon makes grinding, screeching, or rattling noises
- You smell burning or an acrid chemical smell from the unit
- The circuit breaker trips repeatedly when the aircon is turned on
- Water is leaking from the indoor unit onto walls or furniture
- The aircon shows an error code that persists after restart
- Ice keeps forming on the unit even after defrosting
- You have tried all DIY checks and the aircon is still not cold
Delaying professional repair when these symptoms are present can turn a minor and affordable fix into a major and expensive one. A small refrigerant leak costs $50 to $80 to fix now but can destroy a $400 to $1,200 compressor if left unaddressed.
Our Diagnostic and Repair Process
When you call Billy Aircon for a cooling problem, here is what to expect:
Step 1 — Remote assessment: When you contact us, we ask a few questions about the symptoms to narrow down the likely cause. This helps our technician come prepared with the right tools and common replacement parts.
Step 2 — On-site diagnosis: Our technician performs a systematic check covering filters, coils, refrigerant pressure, electrical components, drainage, and thermostat function. We use professional diagnostic tools, not guesswork.
Step 3 — Transparent quotation: Once the cause is identified, we explain the problem to you in plain language and provide an upfront quote for the repair. You approve the cost before any work begins. There are no surprise charges.
Step 4 — Repair: With your approval, we carry out the repair on the spot whenever possible. We carry common parts and refrigerant in our service vehicle, so most repairs are completed in a single visit.
Step 5 — Testing: After repair, we run the aircon for at least 15 minutes, measure the supply air temperature, and confirm that cooling has been fully restored. We do not consider the job complete until your aircon is blowing cold air at the rated performance.
Step 6 — Warranty: All repairs come with a 90-day warranty on parts and workmanship. If the same issue recurs within the warranty period, we return and fix it at no additional cost.
Frequently Asked Questions
How much does it cost to fix an aircon that is not cold? The cost depends entirely on the cause. A dirty filter is fixed with a standard service at $50. A gas top up ranges from $50 to $200. A chemical wash costs $80 to $180. Component replacements like thermistors ($20 to $50), capacitors ($30 to $80), PCB boards ($150 to $400), or compressors ($400 to $1,200) vary by part and brand. We always quote before proceeding.
Can a dirty filter really stop my aircon from cooling? Yes. A severely clogged filter restricts airflow so much that the evaporator coil cannot function properly. In extreme cases, it causes the coil to ice over, which blocks cooling entirely. Regular filter cleaning is the simplest and most cost-effective way to prevent cooling problems.
My aircon is cold at night but not during the day. Why? During the day, your room gains heat from sunlight through windows, heat from walls that face the sun, and potentially from cooking or appliances. This heat load may exceed your aircon’s capacity. At night, without solar heat gain, the same unit cools adequately. Solutions include upgrading to a higher capacity unit, improving insulation, or using blinds and curtains during the day.
Should I repair or replace my old aircon? As a general rule, if the repair cost exceeds 50% of a new unit’s price, or if the unit is over 10 years old and experiencing multiple problems, replacement is usually more cost-effective. New units are significantly more energy efficient, which means lower electricity bills that offset the purchase cost over time.
How quickly can you come to fix my aircon? We offer same-day service for bookings made before 12pm. Afternoon bookings are typically scheduled for the next day. Emergency service is available — contact us and we will do our best to accommodate urgent cases.
Get Your Aircon Cooling Again
A warm aircon in Singapore is more than an inconvenience. It disrupts your sleep, affects your productivity, and makes your home uncomfortable for the whole family. Most cooling problems can be diagnosed and fixed within a single visit by our experienced technicians.
WhatsApp us at +65 9456 5942 to book a diagnosis. Tell us the symptoms, your aircon brand and model if you know it, and your preferred time slot. We will get your aircon blowing cold again as quickly as possible. Serving all HDB estates, condos, and landed properties across Singapore.
