Performed preventative maintenance on the system. Changed filter, cleaned drain, checked coils, tested/inspected all electrical components, checked refrigerant pressures, and tested operation of the system as a whole in both heating and cooling modes. The system is currently operating correctly. I did recommend adding a UV light to prevent the unit from developing growth with in it as almost all units do. Customer agreed it would be a good idea so I installed that while here. This maintenance is now complete the system is currently operating correctly.