Ignoring a frozen coil or chipping the ice off
Ice is a symptom of airflow or refrigerant trouble, and running the unit frozen strains the compressor while the melt can flood the drain pan. Chipping ice bends the soft aluminium fins and can puncture the coil, converting a cleaning job into a major repair. Thaw on fan-only mode and diagnose the cause.
Washing filters but never the coil or blower
Filters catch the coarse dust; the fine shamal fraction sails through and mats onto the wet coil and blower wheel, where a household rinse cannot reach. If airflow stays weak and bills keep climbing despite clean filters, the machinery behind them is the problem, and it needs a chemical wash.
Closing vents in unused rooms to save energy
On a ducted system, closed supply vents raise static pressure in the ductwork rather than saving money: airflow across the coil drops, icing risk rises, and the blower strains. If a room genuinely never needs cooling, the right answer is a damper adjustment at the unit or a zoning setup, not a shut grille.