Arrived on site to perform heating tune up on a 2021 American standard package unit. Client stated no issues. Cycled heater and is operational. Filter was replaced. Blower assembly and whee are good. Inducer motor is in range. All safety switches are good. Found static pressure above range. Temperature rise was in range. Igniter and flame sensor are good. At then end of the visit found unit over heating. Found heat exchanger with hot spots from over heating. Took a look around the house and found 2 vents closed in home and this was causing airflow restriction and is over heating. Opened the vents and unit is operational. Advised they need to stay open in home and filter should be changed out every 3 months. No protection on. It and recommended adding one to protect unit from electrical surges and power outage that can damage or short out Components. Cycled unit and client is aware of how unit is running. Closed unit up and went over how unit is running. Client is aware and happy we cam