Start with safe basic checks
Start with the thermostat mode and temperature. Cooling mode, a sensible set point and a clean remote display rule out many accidental setting changes.
Step 2
Switch off power before inspecting removable filters. A heavily blocked filter reduces airflow and can cause ice to form. Clean only the user-serviceable parts described in the appliance manual.
Step 3
Check whether the outdoor unit starts and whether the circuit breaker has tripped. Do not repeatedly reset a breaker or open electrical panels. Burning smells, exposed wiring and repeated trips need a trained technician.
When to book a technician
If airflow is normal but the room stays warm, the system may have a sensor, capacitor, compressor or refrigerant fault. A technician should test the system rather than topping up gas without finding a leak.
Disconnect power where the manufacturer instructs. Do not open sealed electrical or refrigerant systems without proper training.