Aircon Blowing Hot Air? Here’s What Could Be Wrong

In Singapore’s heat, your aircon isn’t a luxury. It’s a lifeline. So when it starts blowing warm air instead of cooling the room, it’s not just uncomfortable — it’s a sign that the system isn’t working as it should.

Common Reasons Your Aircon Is Blowing Hot Air

1. Thermostat set wrongly or malfunctioning

The simplest check. If settings are wrong — or the thermostat is faulty — the system might be pushing out warm air by mistake.

2. Refrigerant is low

Gas levels that are too low (usually from a leak) mean the system can’t produce enough cooling. The result: air still flows, but it’s not cold.

3. Evaporator coil is frozen or dirty

If the coil inside your indoor unit is frozen over or choked with dust, heat can’t be absorbed properly — so the air stays warm.

4. Compressor isn’t working

The compressor is what drives the cooling process. If it’s weak or failed, refrigerant won’t circulate. No circulation = no cooling.

5. Electrical or PCB faults

Capacitor or relay issues in the outdoor unit can stop cooling functions from activating — even if the indoor unit seems to be working.

6. Air filter is blocked

Restricted airflow means the system struggles to cool air as it passes through. It might feel like the fan is working — but cooling lags behind.

7. Vents or ducts are blocked

Poor air distribution can make it feel like warm air is blowing out, especially in ducted systems or where airflow is unbalanced.

What You Can Check First

• Thermostat mode: set to “cool” or “auto”?

• Filters: clean and clear?

• Cold air ever comes out — or always warm?

• Outdoor unit fan spinning?

If you’ve done these checks and it’s still blowing hot — don’t keep guessing.

Why It Matters

Warm air isn’t a minor glitch. It’s usually a signal of a deeper fault — refrigerant loss, compressor trouble, or coil issues.

If left alone:

• Energy bills rise (as the system keeps trying to cool)

• Faults may worsen (e.g. compressor burnout)

• System lifespan shortens

What starts as warm air can end in full breakdown.

When to Book a Diagnostic

✅ Cooling used to work, but now blows warm

✅ Thermostat and filters already checked

✅ Outdoor unit sounds different or seems inactive

✅ Problem persists even after a reset

Let us check the system fully. We’ll pinpoint the fault — not guess it.