Arrived to do a dual system performance maintenance. Set each system for cooling. Measured each systems static pressure measured a temperature split between return and supply air. Found that the main system is only cooling 10 degrees, and the upstairs system is operating with failing static pressure. Checked interior of the furnace for cleanliness. Found that the main systems blower wheel is coated in dust debris. Went outside and verified each systems refrigerant levels. Found that the main system is low on refrigerant. This indicates a refrigerant leak and can allow the evaporator coil to freeze up. Verified operation of all electronic and mechanical components for each condenser. Found that the contactor for the main system is humming and the capacitor for that system is failing. Rinsed both coils free of debris, and removed the leaves. Spoke with homeowner about the systems. Air conditioning systems are operational at this time.