Denso Air Conditioner Error Code IR

The IR error code on a Denso air conditioner indicates an evaporator fan motor reverse rotation abnormality. Specifically, the control board has detected that the evaporator fan motor is spinning in the wrong direction, registering a reverse rotation signal of approximately -760 rpm. Under normal operation, the evaporator fan motor should spin in a defined forward direction to draw air across the evaporator coil and circulate conditioned air into the space. When the motor rotates in reverse, airflow is disrupted, heat exchange efficiency drops sharply, and the unit cannot function as intended.

This fault is typically detected through a Hall effect sensor or tachometer feedback circuit built into the fan motor assembly. When the control board reads a negative rpm value, indicating reverse shaft rotation rather than the expected positive direction, it triggers the IR code and shuts down or limits operation to protect the system. The root causes generally fall into three categories: a failed or failing fan motor with degraded internal windings or bearings causing erratic rotation, a wiring fault such as reversed phase connections that command the motor to spin backward, or a defective control board that is outputting incorrect drive signals to the motor.

Because the error involves a specific measured signal (-760 rpm), the diagnostic process should focus on confirming actual motor rotation direction, inspecting the motor wiring harness for connection integrity and correct phasing, and testing the motor itself for winding resistance and mechanical freedom. A motor that starts in reverse and cannot self-correct points strongly to a wiring reversal or a failed motor start capacitor or internal component, while a motor spinning freely but receiving incorrect signals points toward the control board.