We performed a comprehensive diagnostic and repair on a Carrier heating and cooling system to address a failure in temperature control. Our team inspected the attic-based furnace components, including the burner assembly, blower wheel, and circuit board, while verifying airflow through the flexible ductwork. We also evaluated the outdoor condenser unit, testing the electrical contactors, capacitors, and the rusted disconnect box to ensure safe and efficient operation. After identifying electrical and mechanical performance gaps, we restored the system's cooling capacity and verified the ecobee smart thermostat settings. This detailed inspection ensured the San Antonio residence returned to a comfortable indoor environment despite the high outdoor temperatures.