Upon my arrival, I performed a six month check up on one straight cool furnace system. Flushed and treated the water removal system, washed the condenser coil using water, cleaned and treated the electrical cabinet with electrical insecticide, then verified system safety and performance. I found that the voltage enhancement system is below manufacturer recommendations and that the refrigerant pressure control is improperly installed metering the refrigerant, causing a high subcool value indicating a restriction. I spoke with the customer about my concerns and he approved repairs on both the refrigerant pressure control and the voltage enhancement system as well as renewing his maintenance agreement. A return will be scheduled by the office.