Came out to perform preventative maintenance on AC system. Discussed with customer about maintenance being provided today, filters, and any issues with the system currently. Customer stated that the filters needed to be changed and they know this system may need refrigerant again this year. I changed the filters out for customer. Inspected the blower assembly, motor, capacitor, evaporator coil, drain and overall condition of equipment in closet. Found oil residue on evaporator coil and made customer aware of the leak in the coil. Washed condenser coil thoroughly. Inspected the compressor, fan motor, capacitor, contactor and electrical wiring. Found minor issues with wiring that I fixed for customer. Cycled the AC on and checked operation, amps, temperatures and pressures. Found system running at a 42 degree superheat and based on my calculations, system needed to be running at 21. Made customer aware of my findings and we discussed options. Customer just wanted to add a pound of refrig