Coolant control method and apparatus for vehicle air conditioning system

摘要

A coolant shutoff valve is closed when a motor-operated temperature door is moved to full cold position to prevent heating of air due to radiation, conduction, convection, or leakage around the door. The motor moves the door to hot or cold limit positions and remains in a stall condition to maintain such positions. A motor control responsive to operator selected temperature moves the door to such limit positions. A shutoff circuit associated with the motor control senses whether a hot or cold mode is selected and detects from the motor current whether the motor is stalled. When the circuit determines both a cold mode and motor stall current an actuation signal is sent to the shutoff valve.