AC performance tune up times one system. Inspect blower, evaporator and ductwork. Changed out filter client supplied. Cast thermostat for proper operations. Check outdoor unit. Refrigerant level good at this time. Test capacitor and contactor. Wash condenser coil. David stated that the auxiliary was engaging too soon when it was cold. I ohmed out the sensor and found it to be weak. Office will check availability and I will return before it gets cold again. System operating at manufacturer specs at this time.