Silver club fall furnace tune up on 2018 Carrier furnace. Asked customer about filter and how unit has worked this summer and filter needs to be replaced, but unit has been working great. Checked and cleaned flame sensor. Cycled system on for preliminary check to test order of operation. Checked flue, evaporator coil, blower and drain. Checked thermostat connections and found heating and cooling lead wires from thermostat to w and y to be loose, so I tightened them down. Cycled system in again and tested blower motor, inducer motor and gas pressure. Replaced gas cap. Checked temperature rise. System is operating well for winter time.