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Error code reference

Mitsubishi Air Conditioner Error Code FN

Fan alarm

Mitsubishi codesMitsubishi air conditioner codes

Fan alarm - cooling fan stopped due to fault, low rotation speed, or different operation from Pr.244 setting.

First step from the service manual

Check the cooling fan for a failure.

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

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What FN means on a Mitsubishi air conditioner

The FN error code on a Mitsubishi air conditioner indicates a cooling fan alarm condition. This fault is triggered when the indoor or outdoor cooling fan motor either stops completely, operates at a rotation speed below the expected threshold, or runs in a manner that conflicts with the behavior defined in parameter Pr.244. The control board continuously monitors fan operation and compares actual performance against programmed settings, so any deviation outside acceptable limits will generate this alarm and typically halt system operation to prevent component damage.

The cooling fan is essential for heat exchange across the evaporator or condenser coil. When the fan fails to move air at the correct speed or stops entirely, refrigerant temperatures and pressures can shift to unsafe levels very quickly. The Pr.244 parameter specifically governs expected fan operation behavior, meaning the fault can also be triggered by a configuration mismatch rather than a purely mechanical failure. This distinction is important during diagnostics because a fan that is physically functional can still trigger FN if the parameter setting does not match the installed fan type or wiring configuration.

Common physical causes include a seized or obstructed fan motor, a failed capacitor on single-phase fan motors, a broken or disconnected wiring harness to the fan motor, and failed bearings causing rotation resistance. Technicians should begin by inspecting the fan blade for physical obstructions and checking whether the motor shaft spins freely by hand. If the motor is free but not starting, capacitor resistance and motor winding continuity should be measured before assuming the motor itself requires replacement.

Source: manufacturer service documentation.

Common causes of FN

  1. 01

    Seized or failed fan motor

    Part replacement

    The fan motor bearings can wear out or seize, preventing the fan from spinning. Attempt to rotate the fan blade by hand with power off. If it is stiff or locked, the motor has likely failed and needs replacement.

  2. 02

    Fan blade obstruction

    Wiring / connection

    Debris such as leaves, dirt buildup, or ice accumulation can physically block the fan blade from rotating at proper speed. Inspect the fan housing and blade for any obstruction and clear it before restarting.

  3. 03

    Failed or weak run capacitor

    Part replacement

    On single-phase fan motors, a failed capacitor prevents the motor from reaching full operating speed or starting at all. Test capacitor capacitance with a multimeter and compare to the rated value printed on the capacitor body.

  4. 04

    Wiring fault or disconnected connector

    Wiring / connection

    A loose, corroded, or broken wire between the control board and the fan motor can interrupt the signal or power supply to the fan. Inspect all connectors and terminals at the motor and the control board for damage or corrosion.

  5. 05

    Pr.244 parameter mismatch

    Wiring / connection

    If the Pr.244 parameter setting does not match the actual fan type or configuration installed in the unit, the control board may flag the fan operation as incorrect even when the fan itself is functioning normally. Review the parameter setting and verify it matches the installed fan specifications.

See the test procedure for each cause

Frequently asked questions about FN

What does FN mean on a Mitsubishi air_conditioner?
The FN error code on a Mitsubishi air conditioner means the cooling fan has stopped, is running below the required rotation speed, or is operating differently than what the Pr.244 parameter setting expects. The system activates this alarm to prevent damage caused by inadequate airflow across the heat exchanger. The unit will typically stop normal operation until the fault is resolved and cleared.
Can I fix the FN error on my Mitsubishi air conditioner myself?
Some causes of the FN error, such as clearing a physical obstruction from the fan blade, can be addressed without professional help. However, diagnosing a failed motor, testing a run capacitor, or adjusting the Pr.244 parameter requires electrical knowledge and the appropriate tools. If you are not comfortable working with electrical components in HVAC equipment, a licensed technician should handle the repair.
Is it safe to keep running my Mitsubishi air conditioner when the FN code is showing?
No, you should not attempt to continue operating the unit while the FN error is active. Without proper fan operation, heat exchange is compromised, which can cause refrigerant pressure to reach unsafe levels and lead to compressor damage. The system is designed to shut down when this fault is detected specifically to prevent more serious and costly damage.
How much does it cost to repair a Mitsubishi FN fan alarm error?
Repair costs vary depending on the root cause. Clearing an obstruction or reseating a connector may cost only a service call fee, typically in the range of $75 to $150. Replacing a run capacitor is generally a low-cost repair, often $100 to $250 including parts and labor. A full fan motor replacement can range from $250 to $600 or more depending on the unit model and motor availability.
Will resetting my Mitsubishi air conditioner clear the FN error code?
A power reset may temporarily clear the FN error code, but if the underlying fault with the fan motor, wiring, or parameter setting has not been corrected, the error will return as soon as the system attempts to operate the fan again. A reset is useful for confirming whether the fault is intermittent, but it should not be treated as a repair. The root cause must be identified and corrected to permanently resolve the alarm.

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