Completing a/c maintenance on two central a/c systems the 1st floor unit is and older R-22 system and the 2nd floor is 410a run tru system. Whole performing the maintenance on the 1st floor air handler there was some visible frost on the coil after checked the system pressures this unit was found to be low on refrigerant. R-22 systems are no longer being manufactured and is recommend to have this unit replaced system is not performing and is past it’s life expectancy. Chemically cleaned evaporator coil. Inspected blower compartment and primary drain pan. Treated and cleared all drain lines,traps and tested all condensate pumps. Brushed and cleaned all electrical cabinets and tighten and secured all electrical connections on both inside and outdoor units. Tested all safety switches all in working condition. Chemically cleaned outdoor condenser and checked operations and refrigerant pressures. Tested all electrical voltage, capacitors, and amperage on all motors and compressors. Syst