I completed a two system heating maintenance. The 16x20x5 and 20x20x5 media filters are still ok but will need to be changed in spring time. I checked the amp draw on the blower motor and heat strips. I checked refrigerant charge and tested defrost cycle on the outdoor units. I checked the amp draw and tested the capacitor on the outdoor units. I tested safeties and confirmed proper sequence of operation. Both systems are currently heating at manufacturers specifications.