Preformed heating maintenance on gas furnace. Checked thermostat went through fault history and confirmed was properly set up and working correctly. Pulled flame sensor and cleaned also inspected all burners for rust and corrosion. Checked pressure switch tubing and found crack and obstruction free. Confirmed all pressure switches are working properly and all safeties are working as should. Checked gas pressure on modulating gas valve 4.0inwc at 30% and 9.8inwc at 100%. Confirmed all high and low voltage is good and tight. Confirmed blower wheel was clean and balanced. Took a amp draw on variable speed blower motor and found within specs 6.8 at 100% blower speed operation. Checked furnace heat exchanger for cracks with nothing found. Replaced customer provided humidifier pad and confirmed operation of by pass humidifier. See no issues or concerns at this time. Returned to service