Mitsubishi Air Conditioner Error Code E.IOH

E.IOH indicates that the resistor in the inrush current limiting circuit has overheated. This circuit protects the unit by controlling the surge of electrical current that occurs each time the system powers on. The most common trigger is turning the unit on and off too frequently without allowing adequate cooling time between starts. If the problem persists without frequent power cycling, a component within the circuit itself may have failed.

You should not continue operating the unit while E.IOH is active. This fault involves the high-voltage power section of the inverter, and running the system with an overheated or degraded inrush resistor risks further damage to the inverter board or other electrical components. Power the unit off and leave it off until the cause is diagnosed and corrected.

Repair costs vary depending on which component has failed. If only the inrush resistor needs replacement, parts and labor costs are typically in the range of $100 to $300. If the bypass relay or inverter board requires replacement, costs can rise to the range of $300 to $800 or more depending on the unit model and local labor rates. A diagnostic visit to confirm the failed component is recommended before committing to any repair.

A reset may temporarily clear the E.IOH code, but the fault will return if the underlying cause is not addressed. If the error was triggered by frequent power cycling, allowing the unit to rest and then performing a single reset may resolve it. However, if a component such as the inrush resistor or bypass relay has failed, the code will reappear on startup and a reset alone will not fix the problem.

Start by ensuring you have not been turning the unit on and off repeatedly in a short period, then allow the unit to rest for at least 30 minutes before attempting a restart. If the error clears and does not return, frequent power cycling was likely the cause. If the error returns, a technician will need to inspect the inrush current limit resistor, the bypass relay, and the inverter board for component-level faults.