Performed semiannual maintenance on one heat pump cooling unit. Inspected all Performance, Mechanical and Safety Systems. While performing the maintenance on the system, I found that the indoor coil is extremely rusted and corroded. I also found that the underside of the coil is dirty which is causing an airflow restriction. The indoor blower wheel is caked over in dirt/dust which is causing a higher electrical amp draw on the motor. Continued my inspection and found that the home has higher levels of humidity, possibly caused by the system not operating at 100% cooling capacity. I recommend replacement of the indoor coil and cleaning of the blower wheel to return the system back to 100% cooling capacity. Flushed and treated the primary drain line that exits outside next to the condensing unit. Verified all other components were operating within manufacture’s specifications for operation.