Why Is Your Aircon Not Cold?
You set the temperature to 24 degrees, hear the aircon running, but the room stays warm. This is one of the most frustrating aircon problems — and one of the most common calls Billy Aircon receives from homeowners across Singapore.
An aircon that is not blowing cold air does not always mean a major breakdown. In many cases, the fix is straightforward and affordable. But ignoring the problem leads to higher electricity bills, compressor damage, and eventually a complete system failure.
This guide walks you through the most common causes of an aircon not cooling, DIY checks you can do before calling a technician, and when professional repair is necessary.
Common Causes of Aircon Not Blowing Cold Air
1. Dirty or Clogged Air Filter
The air filter is the first line of defence against dust, pet hair, and airborne particles. When it becomes clogged, it restricts airflow over the evaporator coil. Reduced airflow means less heat is absorbed from the room, resulting in warm air blowing from your aircon.
How to check: Open the front panel of your indoor unit and slide out the air filter. Hold it up to light — if you cannot see through it, it needs cleaning.
DIY fix: Remove the filter and rinse it under running water. Let it dry completely before reinstalling. Do this every 2 to 4 weeks in Singapore’s dusty, humid environment.
This is the single most common cause of reduced cooling and the easiest to fix yourself. If regular filter cleaning does not restore cooling, the problem lies deeper.
2. Low Refrigerant (Gas)
Refrigerant is the substance that absorbs heat from indoor air and transfers it outside. When the refrigerant level drops due to a leak, your aircon cannot effectively cool the air. The symptoms are distinctive: the aircon runs continuously but the air coming out is only slightly cool or lukewarm.
How to check: Feel the copper pipes connecting your indoor and outdoor units. If the thicker pipe (suction line) is not cold to the touch, or if you see ice forming on it, low gas is likely the cause.
Professional fix needed: A gas top up from Billy Aircon includes leak detection to find and address the source of the gas loss. Without fixing the leak, the gas will escape again within weeks.
3. Dirty Evaporator Coil
Even with regular filter cleaning, fine dust particles 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 effectively absorbing heat from the air.
How to check: Open the front panel and look at the coil behind the filter. If it appears grey, brown, or black instead of silver, it is dirty enough to affect cooling.
Professional fix needed: A chemical wash uses alkaline solution to dissolve and flush away the accumulated grime, restoring the coil’s heat exchange capability.
4. Frozen Evaporator Coil
A frozen evaporator coil is a secondary problem caused by either low refrigerant, restricted airflow (dirty filter), or a malfunctioning blower fan. When ice forms on the coil, it completely blocks airflow and the aircon blows room-temperature air.
How to check: Open the front panel. If you see ice or frost on the coil surface, the evaporator is frozen.
DIY first step: Turn off the aircon and let the ice melt completely — this takes 2 to 4 hours. Clean the filter. Turn the aircon back on. If ice forms again within a day, there is an underlying issue that needs professional diagnosis.
5. Faulty or Weak Compressor
The compressor is the heart of your aircon system. It pumps refrigerant between the indoor and outdoor units. A failing compressor cannot generate enough pressure to circulate refrigerant effectively, resulting in poor cooling.
How to check: Go to your outdoor unit. If the compressor is running but making unusual clicking, rattling, or grinding sounds, it may be failing. If the outdoor unit’s fan is spinning but the compressor is completely silent, it may have tripped on a safety switch or failed entirely.
Professional fix needed: Compressor issues require a trained technician to diagnose. Depending on the severity, the fix may range from replacing a capacitor ($80–$150) to replacing the compressor ($800–$1,500) or recommending a new unit entirely.
6. Faulty Thermistor or Temperature Sensor
The thermistor measures room temperature and tells the aircon when to cycle the compressor on and off. A faulty thermistor may give incorrect readings, causing the compressor to shut off prematurely — before the room reaches the set temperature.
How to check: Set your aircon to its lowest temperature (16°C) in cooling mode. If the compressor runs briefly then stops even though the room is still warm, a faulty thermistor could be the cause.
Professional fix needed: Thermistor replacement is a quick repair that Billy Aircon can complete in a single visit.
7. Blocked or Leaking Ductwork (Ducted Systems)
For ducted aircon systems found in some condos and landed homes, cold air can escape through holes, gaps, or disconnected sections in the ductwork. This means the cooled air never reaches your rooms even though the unit is working properly.
Professional fix needed: Ductwork inspection and repair requires accessing ceiling voids and checking every section of the duct run.
8. Wrong Aircon Mode or Settings
Sometimes the simplest explanation is the correct one. Your aircon may be set to “fan only” mode instead of “cool” mode, or the temperature setting may be higher than the current room temperature.
How to check: Look at your remote control display. Ensure the mode is set to the snowflake symbol (cooling mode), not the fan symbol. Set the temperature to at least 2 degrees below the current room temperature.
DIY Troubleshooting Checklist
Before calling a technician, run through these quick checks. They take 10 minutes and can save you a service call fee.
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Check the remote control: Is it set to cool mode (snowflake icon)? Is the temperature set below room temperature? Are the batteries fresh?
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Check the air filter: Remove and inspect it. If dirty, wash with water and let it dry before reinstalling.
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Check the airflow: Are curtains, furniture, or shelves blocking the indoor unit’s air outlet or intake? Ensure at least 15 cm of clearance on all sides.
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Check the outdoor unit: Is the condenser running? Is the fan spinning? Is the area around it clear of obstructions? Leaves, laundry, or boxes placed too close to the condenser restrict airflow.
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Reset the system: Turn off the aircon at the isolator switch (not just the remote). Wait 5 minutes. Turn it back on. This can clear minor electronic glitches.
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Check for ice: Open the front panel and look for frost on the evaporator coil. If present, turn off the unit and let it defrost completely.
If none of these steps restore cooling, the problem requires professional diagnosis.
When to Call Billy Aircon
Call us when:
- Your aircon is still not cold after cleaning the filter and checking settings
- Ice keeps forming on the evaporator coil even after defrosting
- The outdoor unit’s compressor is not running or making unusual noises
- You notice a refrigerant leak (hissing sound, oily residue around pipe joints)
- Your aircon trips the circuit breaker when it starts
- The problem has been getting worse over several days or weeks
Billy Aircon’s technicians diagnose the issue on-site and provide a transparent quote before starting any repair. We carry common spare parts on our service vehicles so most repairs can be completed in a single visit.
Our Diagnostic and Repair Process
Step 1: Our technician inspects the indoor and outdoor units, checks refrigerant pressure, electrical connections, and component condition.
Step 2: We identify the root cause and explain it to you in plain language. No jargon, no scare tactics.
Step 3: We provide a written quote for the repair. You decide whether to proceed.
Step 4: If approved, we carry out the repair on the spot whenever possible. Complex repairs may require a follow-up visit for parts.
Step 5: We test the system thoroughly and confirm that cooling is restored to the correct temperature range.
All repairs come with Billy Aircon’s 90-day warranty. If the same issue recurs within 90 days, we fix it at no extra charge.
Frequently Asked Questions
How much does it cost to fix an aircon that is not cold?
It depends on the cause. A filter cleaning is free (DIY). A gas top up ranges from $50 to $200. A compressor replacement can cost $800 to $1,500. Billy Aircon provides a clear quote after on-site diagnosis.
Should I keep running my aircon if it is not cold?
It is best to turn it off until the issue is diagnosed. Running a gas-starved or malfunctioning aircon puts stress on the compressor and can turn a minor repair into a major one.
How do I prevent my aircon from losing cooling performance?
Regular servicing every 3 months, quarterly filter cleaning, and an annual chemical wash keep your aircon running at peak performance.
Can a dirty aircon make me sick?
Yes. A neglected aircon accumulates bacteria and mould that get blown into your room. This can trigger respiratory issues, allergies, and skin irritation — especially in Singapore’s humid climate.
Get Your Aircon Cold Again
Billy Aircon fixes aircon cooling problems fast. With same-day appointments, experienced technicians, and a 90-day warranty on all repairs, we get your home comfortable again.
WhatsApp us at +65 9456 0875 to describe your aircon issue. We respond within 24 hours and can usually schedule a diagnostic visit within the same day.
