Den Appliances Aircon Not Cooling? 8 Common Causes and What to Do
Your aircon is running but the room isn't getting cold. Here's how to find the likely cause, what you can safely check yourself, and when it needs a technician.
Work through the causes below in order. The first three you can check yourself in a few minutes. The rest need a technician with gauges and electrical testing tools.
| Cause | Signs | Can you fix it? |
|---|---|---|
| Wrong mode or setting | Fan or dry mode selected, or temperature set above room temperature | Yes. Select cool (snowflake) and set 2–3°C below room temperature |
| Dirty indoor filters | Weak airflow, dusty smell, ice on the indoor coil | Yes. Wash the filters in lukewarm water and let them dry |
| Blocked or dirty outdoor unit | Outdoor fan running but coil covered in dust, leaves or salt | Partly. Clear plants and debris. A proper coil clean is a service job |
| Low refrigerant (gas leak) | Cools weakly, then gets worse; ice on pipes; hissing | No. The leak must be found and repaired before regassing |
| Failed capacitor | Outdoor unit hums but fan or compressor won't start | No. Electrical work for a technician |
| Outdoor fan motor | Outdoor fan doesn't turn; unit cuts out on high pressure | No |
| Sensor or inverter board fault | Error code on display; unit starts then stops | No |
| Compressor failure | Outdoor unit runs but no cooling at all; loud knocking | No. On older units, replacement may be better value |
Checks You Can Do Yourself
- Check the remote. Make sure it's on cool mode (snowflake icon), not fan, dry or auto, and the set temperature is below the room temperature. Replace the batteries if the display is faint.
- Clean the filters. Switch the unit off, lift the front cover, slide out the mesh filters and rinse them in lukewarm water. Let them dry fully before refitting. During heavy use, do this every 2–4 weeks.
- Look at the outdoor unit. Is the fan spinning? Is the coil blocked by plants, leaves, a cover or a build-up of dust or salt? Clear anything around it and leave at least 30 cm of space.
- Give it 15 minutes. Inverter aircons ramp up gradually. Close windows and doors and give it time before deciding it isn't cooling.
Don't: open the outdoor unit's electrical cover, try to "top up" gas yourself, or keep resetting a unit that trips the breaker. These need a qualified technician.
Why Coastal Aircons Lose Cooling Faster
Along the Atlantic Seaboard, False Bay and the Gqeberha beachfront, salt in the air settles on the outdoor unit's aluminium fins and copper pipes. Over time this blocks airflow and corrodes the coil and electrical connections, and cooling drops off gradually.
If you live close to the sea, service the aircon at least every six months. See our guide on protecting aircons from salt air.
Is Regassing the Fix?
An aircon is a sealed system. It only runs low on gas if there's a leak. A regas without finding the leak works for a while, then the problem comes back. A proper repair finds and fixes the leak, then refills to the manufacturer's specification.
When to call a technician
- You've cleaned the filters and set the right mode, and it still blows warm air
- The outdoor unit hums but the fan doesn't turn
- There's ice on the pipes or the indoor coil
- The display shows an error code
- The breaker trips when the aircon starts
Call or WhatsApp 064 067 4863 with the make and model, the symptoms, any error code and your suburb. More than 10 years' experience across Cape Town and Gqeberha.
FAQs
Why is my aircon running but not cooling?
Usually because of dirty filters, the wrong mode, a blocked outdoor unit, low refrigerant from a leak, or a failed capacitor or fan motor. Check the mode, filters and outdoor unit first. If it still doesn't cool, a technician needs to test the gas pressure and electrical parts.
How often should an aircon be serviced in Cape Town?
Once or twice a year for most homes, ideally before summer. Units close to the sea should be serviced at least every six months because salt air builds up on the outdoor coil.
Can I regas my aircon myself?
No. Handling refrigerant needs specialist equipment and training, and adding gas without fixing the leak is only a temporary fix.
Why does my aircon cool at night but not during the day?
This often means the unit is undersized for the room, the outdoor unit is in direct afternoon sun with poor airflow, or it's slightly low on gas. A technician can check the pressures and sizing.
Book a repair or request a quote
Call or WhatsApp with your appliance type, make and model, the fault or error code, and your suburb. More than 10 years' experience across Cape Town and Gqeberha.