Aircon Not Cooling? 8 Common Causes and What to Do in Singapore
- ✍️ By City Cooling Management
- 🏷 Aircon Repair · Aircon Servicing · Maintenance
In Singapore’s year-round heat, an aircon that isn’t cooling is more than an inconvenience — it’s an urgent problem. Before you call for a repair or assume the worst, it helps to understand what’s actually causing the issue.
Some causes are minor and fixable in minutes. Others require a technician and, in some cases, a unit replacement. Here’s a complete breakdown of the 8 most common reasons your aircon is blowing warm or insufficiently cold air — and what to do about each.Each breakdown will tell you when is best time to opt for a professional aircon repair service in Singapore and get expert advice.
1
Dirty or Blocked Air Filter
What’s happening: The air filter traps dust and particles from the air before it passes over the evaporator coil. When the filter is heavily clogged, airflow is severely restricted — the unit can’t pull enough air across the coil to cool it, and what comes out feels weak and warm.
How to check: Slide out the filter panel on your indoor unit. If the filter is visibly grey, dark, or matted with dust, it needs cleaning.
What to do: Rinse under running water, allow to dry completely, and reinstall. This is the one maintenance step every homeowner should do themselves monthly.
When to call a technician: If cleaning the filter doesn’t improve cooling within 30 minutes, the issue lies elsewhere.
2
Low Refrigerant (Gas) Levels
What’s happening: Refrigerant (commonly R410A or R32 in modern Singapore units) is the substance that absorbs heat from indoor air and transfers it outside. If the gas level drops — usually due to a leak — the cooling process is compromised. The unit blows air, but it doesn’t get cold.
How to check: You cannot check refrigerant levels yourself. Signs include: room takes unusually long to cool, ice forming on the indoor unit’s piping, or a hissing sound near the indoor unit.
What to do: Do not attempt to top up gas without locating and repairing the leak first. Adding gas to a leaking system is a temporary fix that wastes money and can damage the compressor.
When to call a technician: Immediately. A gas leak left unaddressed damages compressor bearings and can lead to a full system failure.
3
Dirty Evaporator Coil (Fan Coil)
What’s happening: The evaporator coil is where refrigerant absorbs heat from the air. When the coil is coated in dust and grime (which happens over months in Singapore), heat exchange efficiency drops dramatically — the unit works harder but delivers less cooling.
How to check: If your filter is clean but airflow still feels weak, the coil is the likely culprit.
What to do: A dirty evaporator coil requires a professional chemical wash or, in severe cases, a full chemical overhaul to restore performance.
When to call a technician: Schedule a chemical wash if the last service was more than 6 months ago.
4
Faulty or Tripped Thermostat/PCB
What’s happening: The PCB (Printed Circuit Board) is the brain of your aircon. It controls temperature sensing, compressor operation, fan speed, and all functions. A faulty PCB can cause incorrect temperature readings, preventing the compressor from running at the right capacity — or at all.
How to check: If your unit appears to be running (fan is on, display is lit) but no cold air comes out whatsoever, and the filter and gas levels are fine, a PCB fault is possible.
What to do: This requires a technician to diagnose with a multimeter and error code reader.
When to call a technician: Immediately — PCB replacement is not a DIY fix.
5
Blocked or Dirty Condenser (Outdoor Unit)
What’s happening: The outdoor condenser is responsible for releasing the heat absorbed from your home to the outside air. If the condenser fins are blocked with dust, leaves, or debris — or if the outdoor unit is in a poorly ventilated location — heat can’t escape efficiently, and cooling performance degrades.
How to check: Look at your outdoor condenser. Is there visible dirt on the fins? Is it surrounded by walls, boxes, or objects on multiple sides with no airflow clearance?
What to do: Do not hose the condenser yourself without turning off the unit at the isolator. Professional condenser cleaning is recommended.
When to call a technician: If the outdoor unit is making unusual noise, has ice forming, or is visibly caked with dirt.
6
Compressor Failure
What’s happening: The compressor is the heart of your aircon system — it pressurises refrigerant to enable the cooling cycle. When a compressor fails, the fan may still run but there is zero cooling. Compressor failure is the most expensive repair in any aircon system.
Signs of compressor failure:
Unit runs but produces no cold air at all
Outdoor unit is silent when the indoor unit is on
Loud banging or grinding from the outdoor unit
Circuit breaker trips when the aircon is switched on
What to do: Get a technician to confirm compressor failure before taking any action. In many cases, if the unit is over 8–10 years old, replacing the entire system is more cost-effective than replacing the compressor alone.
7
Refrigerant Pipe Leak or Insulation Damage
What’s happening: Refrigerant pipes run between your indoor and outdoor units. If the pipe develops a leak, or if the insulation wrapping deteriorates and allows the cold pipe to sweat and lose efficiency, cooling performance drops.
How to check: Wet patches along the pipe run (from condensation on uninsulated pipes) or visible damage to the pipe insulation cladding.
What to do: Pipe inspection and reinsulation is part of a thorough service visit.
8
Undersized Unit for the Room
What’s happening: If your aircon has never cooled the room to a comfortable temperature — even when new — the unit may simply be undersized for the space. This is common in renovated rooms where walls were removed to create larger open-plan spaces, but the original single-room aircon was retained.
What to do: Ask a technician to calculate the required BTU for the actual room size and compare with your current unit’s capacity.
Repair or Replace? A Singapore Homeowner's Guide
| Scenario | Recommendation |
|---|---|
|
Unit is under 5 years old, single part failure
|
Repair
|
|
Compressor failure, unit is 5–8 years old
|
Get quotation for both repair and replacement
|
|
Compressor failure, unit is over 8 years old |
Replace
|
|
Multiple faults appearing repeatedly
|
Replace
|
|
Energy bills rising despite regular servicing
|
Replace with inverter model
|
|
Unit no longer available for parts
|
Replace |
City Cooling Engineering provides same-day and next-day repair services for all major aircon brands. Our BCA-certified technicians carry common spare parts and refrigerants on every service van, minimising the need for a second visit.
With years of experience under our belts, City Cooling provides top-notch professional aircon repair and maintenance services. Contact us today to set up an appointment with our team.
Frequently Asked Questions (FAQs)
Why is my aircon blowing cold air for 10 minutes then warm air?
Can I fix an aircon compressor myself?
How much does aircon repair cost in Singapore?
My aircon was repaired last month and it's already not cooling again. What's wrong?
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