Performed a heating maintenance on a 2020 Lennox unit. Cleaned and Adjust Burners. Check Combustion Air for Proper Venting. Examine the Heat Exchanger for Damage / Corrosion. Test Furnace Safety Controls. Inspect Gas Piping. Tighten Electrical Connections. Measure the Voltage and Amperage. Flush the Condensate Drains. Measure Tempurature Difference between Supply and Return Air. Vacuum Furnace Return Grille. Adjust Gas Pressure & Pilot. Clean in-place Blower Compartment. Inspect Blower Wheel for Proper Balance. Check the System's Static Pressures to Ensure Proper Airflow. Inspect Duct Connections for Air Leaks / Sizing / Insulation. Check all System Safety and Limit Switches. Clean Flame Sensor. Inspect Carbon Monoxide Detector. Check Thermostat for Proper Operation / Calibration. Found the thermostat wire coming into the furnace had been damaged. Unsure if wether it was a rat or wear a tear. Client was informed of the finding and in the current moment does not want to replace it. Fil