An air conditioner that hums away but never cools the room is one of the more frustrating faults — partly because the cause could be electrical, mechanical or just a dirty filter. Here is how to tell which.
If it's silent or trips the power → electrical
If the outdoor unit isn't running, the breaker keeps tripping, or you hear nothing from the compressor, the cause is usually electrical: an undersized or shared circuit, a failing capacitor, a faulty isolator, or a compressor drawing too much current. This is an electrician's job — see the aircon electrical guide.
If it runs but blows weak/warm air → airflow or gas
- Dirty filter or coils — the easiest check; choked airflow means it runs but barely cools.
- Low refrigerant gas — needs an HVAC technician to find the leak and recharge.
Why we check the electrical side first
Electrical causes — a tripped circuit, a dead capacitor, a faulty isolator — are common and quick to confirm, and they're exactly what stops the compressor from running at all. We test the circuit and isolator with fault finding before anyone assumes an expensive compressor or gas problem.
Get it diagnosed
We sort the electrical faults and tell you honestly when it's an HVAC (gas/coil) job. Book a callout or see our electrical services.