Arrived to do a performance maintenance. Set system for cooling. Measured the systems static pressure and measured a temperature split between return and supply air. Checked interior of the furnace for cleanliness. Found that the evaporator coil is impacted with debris and the blower wheel is coated in dust debris. Went outside and verified refrigerant levels. Found that the evaporator coil is operating right at freezing. This can indicate an airflow issue or the system could be leaking refrigerant. Judging by the debris in the evaporator coil and on the blower wheel determined charge is off due to airflow restrictions. Verified operation of all electronic and mechanical components. Rinsed coil free of debris. Spoke with homeowner about the system. Air conditioning system is operational at this time.