Why Is My Aircon Not Cooling? 7 Common Causes (and Fix Costs)

The quick answer

If your air conditioner runs but will not cool, the usual culprits in Perth homes are a dirty filter, low refrigerant from a leak, a failed capacitor, or a unit that is simply too small for the room. Some are a five-minute fix; others need a licensed tech.

1. Dirty or blocked filters

A clogged filter chokes airflow, so the room never cools and the unit can ice up. Pull the front cover, wash the filters, let them dry and refit. Do this every couple of months over summer. Cost: free.

2. It is overdue a service

Dust on the indoor coil and a slimed-up drain quietly kill performance. A professional service and clean brings it back. Cost: around $229 per unit.

3. Low refrigerant (a leak)

If it blows cool-ish but never cold, you may be low on gas — and because a sealed system does not use gas up, that means a leak. Topping up without fixing the leak wastes money. We find and fix the leak, then recharge. See re-gas.

4. A failed run capacitor

A cheap part that starts the compressor and fan. When it fails the unit hums but will not cool. A clamp-meter test confirms it, and it is usually a same-visit fix.

5. Compressor or fan motor fault

The bigger-ticket items. A fault diagnosis tells you exactly what failed and what it costs to fix — before any work starts.

6. Thermostat or controller issue

Wrong mode, flat remote batteries or a faulty controller can all stop cooling. Always worth checking before you call.

7. The unit is too small

An undersized system runs flat out and still loses on a 40-degree day. Check the right size with our size calculator.

When to call

If a filter clean and a controller check do not fix it, book a fault diagnosis. You get a fixed price before we start — no surprises.