HVAC Diagnosis Made Easy: Blend Door, Blower, and A/C Testing With a Bidirectional Scanner

LIVE DATA WE LOOK AT Blend door actuator commanded position versus actual position Mode door and recirculation door position feedback Evaporator temperature sensor In car temperature sensor and ambient air temperature sensor Sunload sensor A/C refrigerant pressure sensor reading in PSI or voltage Blower motor commanded speed and blower control voltage A/C compressor clutch or compressor control request status Engine coolant temperature, which the module uses before it allows full heat ACTIVE TESTS AND BIDIRECTIONAL CONTROLS DEMONSTRATED Commanding the blend door actuator from full cold to full hot and listening for movement Cycling the mode doors between panel, floor, and defrost Commanding the recirculation door open and closed Running the blower motor through low, medium, and high speeds Commanding the A/C compressor clutch or compressor relay on and off Commanding the cooling fans on to verify condenser airflow Actuator calibration or relearn after a repair, which many vehicles require