Start with the accessible filter
Turn the system off and follow the manufacturer instructions for removing the filter. If it is dusty, wash and dry it as directed before reinstalling it. Clean filters support airflow and normal operation.
Look and listen
Check for visible dust around the louvres, a musty smell on startup, weak airflow, water dripping from the indoor head or unusual sounds. These observations do not diagnose a fault, but they tell you what to investigate.
Book before the rush
If the filter is clean but the signs remain, an internal deep clean or technician inspection may be appropriate. Booking before peak heat means you are not reacting under pressure.
The practical takeaway
A filter check is the right first step. It is also a useful point to decide whether the rest of the indoor unit needs professional attention.