Mitsubishi Air Conditioner Error Code E.OHT

E.OHT indicates that an external thermal relay or a motor-internal thermal relay has been triggered, sending an overheat signal to the control system. The unit shuts down automatically to protect the motor from heat-related damage. The fault is detected through one of the programmable input terminals, which is assigned the OH function via parameters Pr.178 to Pr.189.

No. The E.OHT fault is a protective shutdown, meaning the system has already stopped operation to prevent damage. Attempting to bypass the fault and continue running the unit risks burning out the motor windings, which can result in a much more costly repair. The fault should be diagnosed and resolved before the unit is returned to service.

A technician will first inspect the motor for signs of overheating such as discoloration or unusual odor, then verify that the OH signal is correctly assigned in parameters Pr.178 to Pr.189. They will also test the thermal relay for proper operation and reset behavior, check motor winding resistance, and inspect all wiring in the OH signal circuit for shorts or loose connections.

Resetting the unit may clear the fault temporarily if the thermal relay has cooled and reset on its own, but it will not address the underlying cause. If the motor overheated due to restricted airflow or high load, those conditions must be corrected before restarting. Repeated trips after resetting are a strong indicator that a component inspection is needed.

Repair costs vary depending on the root cause. A wiring correction or parameter adjustment typically costs between $75 and $200 in labor. Replacing a faulty thermal relay generally runs $100 to $300 including parts and labor. Motor replacement is the most expensive scenario, often ranging from $400 to $900 or more depending on the motor type and system configuration.