Air filter restriction
When dust loads the return-air filter, the indoor fan may still run but distribute less air over the coil. This can reduce comfort and, under certain conditions, contribute to icing. We check airflow and coil condition before attributing poor cooling to refrigerant loss.
A filter should be cleaned or replaced according to the appliance manual. A persistent airflow problem can also arise from a dirty blower wheel or obstructed coil, which requires more than surface dusting.

