Follow this AC maintenance checklist before turning on your air conditioner for the season to avoid harming your HVAC system. Start by cleaning the condenser coils, which makes it easier for the air conditioner to remove heat from the air. Check the insulation on the coolant line. Shut off the furnace humidifier. Check the fan. Replace the air filter. Visit the Sears Home Services blog for more HVAC maintenance tips and tips to avoid HVAC repairs.