Mitsubishi Air Conditioner Error Code E.THM

E.THM indicates that the electronic thermal overload relay within the drive has tripped due to detected motor overheat. The protection circuit determined that the motor was operating under overload conditions or was not receiving sufficient cooling while running at low speed. The system shuts down automatically to protect the motor from winding damage. A technician should check the mechanical load on the motor and confirm the Pr.71 parameter is set correctly for the installed motor.

No, you should not continue operating the unit while this fault is active. The E.THM error indicates the motor protection circuit has already tripped the system to prevent overheating. Bypassing or repeatedly resetting the fault without addressing the root cause can lead to permanent motor winding failure and create a potential fire or electrical safety hazard.

Pr.71 is the Applied Motor setting in the drive's parameter configuration. It tells the drive what type of motor is connected, which directly affects how the electronic thermal overload relay calculates the motor's thermal model and protection thresholds. If Pr.71 is set incorrectly, the thermal protection curve will not match the actual motor, causing either premature E.THM trips or insufficient protection against real overheating.

You can reset the fault after the motor has cooled down, but resetting alone will not fix the underlying cause. If the overload condition or cooling issue is not corrected, the fault will return, often in a shorter time as thermal accumulation restarts. Resetting without diagnosis risks repeated trips and eventual motor damage.

Repair cost depends heavily on the root cause. If the fix involves correcting a parameter setting like Pr.71, the cost may be limited to a service call fee, typically in the range of $75 to $200. If the motor requires replacement, parts and labor combined can range from $300 to $900 or more depending on the motor size and unit model.