Arrived to furnace maintenance. Upon arrival I turned the upstairs thermostat off and made my way downstairs to the furnace. Here I checked for proper blower operation/cleanliness, the filter was in good condition and did not replaced. I cleaned the flame sensor and replaced the humidifier pad with one the customer had on hand. The igniter was performing within spec. I then turned the basement thermostat to heat. The cleaned flame sensor was performing within spec and the combustion analysis was proper. While performing these checks however the furnace kicked off due to it overheating. This was because even though I had the downstairs calling for heat the zone damper for this zone was stuck closed and not allowing proper airflow. The damper was receiving proper communication from the zone board but the motor itself had failed. I went over the repair with the customer and with his approval I retrieved a new damper and motor from CD Jones and replaced this. I then tested both zones with