Abstract: Refrigeration system control systems and methods for protecting a refrigerant motor/compressor, for example in an air conditioner, against conditions of excessive loading. The systems and methods of the invention recognize and distinguish between conditions of high operating load and insufficient condenser airflow, and take appropriate action for each. High operating load conditions are responded to by providing a motor/compressor cool-down interval, followed by a restart, so that an air conditioner remains operating at its maximum capacity, consistent with the field conditions. Insufficient condenser airflow conditions are responded to by eventually terminating operation of the motor/compressor until, for example, a service technician is called. Operation is based on a recognition that excessive loading conditions are manifested much sooner when the cause is insufficient condenser airflow than when the cause is a high operating load.