Preformed system maintenance on up and Downstairs systems. Customer systems had dampers installed so I opened the duct leading to a bed room and slightly closed off to the main area where the thermostat is located. Both systems where very dirty and recommended the customer wash the condenser coils at the time of filter change. Also recommended norr frequently changing of the filters. Both systems refrigerant levels are good with an upstairs differential of 18 degrees and Downstairs of 17. The electrical readings where all in normal operating range. I did note a lot of sweating on the duct and plenum box, tracked the issue to a poor air seal on the system leaking cold air onto the warm metal causing the sweat. Customer approved seal and I taped and masticed the unit to prevent air leaks.