A system and method includes at least one heat exchanger, a ram fan, and a controller. The ram fan is driven by a motor. A motor control circuit is configured to provide power to the motor to drive the ram fan. The ram fan is configured to provide a ram flow through the at least one heat exchanger from a ram air inlet. The controller is configured to determine a blockage level of the at least one heat exchanger based on the power to the motor, a speed of the ram fan, and a temperature of the ram flow at the ram fan.