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Error code reference

Mitsubishi Air Conditioner Error Code E.IOH

Inrush current limit circuit fault

Mitsubishi codesMitsubishi air conditioner codes

Inrush current limit circuit fault - resistor of inrush current limit circuit overheated.

First step from the service manual

Check that frequent power ON/OFF is not repeated.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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  • Step-by-step tests with expected resistance, voltage, and continuity values
  • Wiring diagram references and connector pinouts from the OEM service manual
  • Verified part numbers when replacement is required
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What E.IOH means on a Mitsubishi air conditioner

The E.IOH error code on a Mitsubishi air conditioner indicates a fault in the inrush current limiting circuit, specifically that the resistor within that circuit has overheated. Inrush current limiters are thermistors or fixed resistors placed in the main power path to suppress the large surge of current that flows when the unit is first powered on. This surge, often many times the normal operating current, occurs as the capacitors in the inverter or power supply circuit charge from zero. The limiting resistor absorbs this energy briefly before a bypass relay engages to remove it from the circuit during normal operation.

When the unit is powered on and off repeatedly in a short period, the inrush resistor must absorb surge energy each time without sufficient cooling intervals between cycles. This repeated thermal stress causes the resistor to overheat, triggering the E.IOH fault. The control board detects this condition through a thermal sensor or through monitoring the resistor's operating parameters. This is why the first diagnostic step is to confirm that frequent power cycling is not occurring, whether from a user habit, an automated control system, or a fault in another component that is causing repeated restarts.

If rapid power cycling is ruled out, the fault may point to a degraded inrush current limit resistor that can no longer handle normal startup loads, a failed bypass relay that leaves the resistor in circuit continuously during operation, or a fault in the control board circuitry that monitors the resistor. Any of these conditions requires component-level inspection and likely part replacement by a qualified technician, as this circuit is part of the high-voltage section of the inverter board.

Source: manufacturer service documentation.

Common causes of E.IOH

  1. 01

    Frequent power ON/OFF cycling

    Wiring / connection

    Repeatedly turning the unit on and off in a short timeframe prevents the inrush resistor from cooling between startup surges, causing it to overheat. Check thermostats, smart home schedules, or user habits that may be triggering rapid restarts.

  2. 02

    Degraded or failed inrush current limit resistor

    Part replacement

    Over time, the resistor can degrade and lose its ability to handle even normal startup current loads, causing it to overheat under conditions that previously would not trigger the fault. The resistor must be measured and replaced if out of specification.

  3. 03

    Failed bypass relay

    Part replacement

    A relay is normally responsible for bypassing the inrush resistor once the unit has started. If this relay sticks open or fails to engage, the resistor remains in the power path during normal operation and will overheat. Inspect the relay for proper operation and continuity.

  4. 04

    Inverter board fault causing repeated restarts

    Part replacement

    A fault elsewhere on the inverter or control board can cause the unit to repeatedly attempt to start and reset, subjecting the inrush resistor to multiple surge events in rapid succession. Review the fault history for accompanying error codes that may point to a root cause.

  5. 05

    Control board monitoring circuit fault

    Part replacement

    If the circuitry on the control board that monitors the inrush resistor's thermal condition is faulty, it may trigger an E.IOH fault even when the resistor is within safe operating limits. This is a less common cause and is typically diagnosed after all other causes are ruled out.

See the test procedure for each cause

Frequently asked questions about E.IOH

What does E.IOH mean on a Mitsubishi air_conditioner?
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.
Will resetting the unit clear the E.IOH error?
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.
Is it safe to keep running my Mitsubishi air conditioner when E.IOH is displayed?
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.
How do I fix the E.IOH error on my Mitsubishi air conditioner?
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.
How much does it cost to repair an E.IOH fault on a Mitsubishi air conditioner?
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.

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