Upon my arrival I performed a 6 month checkup on 2 heat pump systems. Flushed and treated the water removal systems, washed condenser coils using water, cleaned and treated the electrical cabinets with electrical insecticide then verified system safety and performance. I found the upstairs system operating to within manufacture specifications at this time. The down stairs unit I found it showing signs of low refrigerant charge. I spoke with the customer about adding refrigerant and he approved to do so. As I started to add refrigerant I found that the low side pressures became very high, superheat dropped very low and the sub cooling stayed the same. I quit adding refrigerant at this point and found that the refrigerant pressure control is not metering refrigerant properly. I went over my concerns with the customer and the age of the equipment. He is going to have to think about what he would like to do and is currently going to limp the system along. I did not charge for the refrigera