Diagnosed Goodman furnace (50+ years old) with no heat condition. Found unit short cycling and locking out due to overheating. All components tested operational, but identified high limit switch activation caused by restricted airflow. Recommended continuous fan operation at thermostat and replacement of thick filter with maximum MERV 7 rating. Observed temperature stress points on heat exchanger and intermittent shutdown possibly related to gas valve closure or voltage fluctuations. Scheduled follow-up for complete furnace replacement due to age and condition.
