F2
Mitsubishi Electric Indoor Humidity Sensor or Additional Thermistor Fault (model-dependent)

Indoor unit displays F2, operation stops

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Open or short in humidity/auxiliary sensor, Sensor disconnected from PCB, Damaged sensor harness, Faulty indoor PCB sensor input

How to Fix / Troubleshooting

Safety first: Isolate power at the breaker before opening the unit.

Steps:

  • Identify sensor: On models with humidity or additional sensors, locate the small sensor module in the return air area or on the PCB.
  • Check connection: Ensure the sensor plug is firmly connected to the indoor PCB.
  • Inspect wiring: Look for damage or corrosion on the sensor wires.
  • Replace sensor: If the sensor is physically damaged or tests out of specification, replace it with the correct Mitsubishi Electric part.
  • PCB replacement: If a new sensor does not clear F2, the indoor PCB may be faulty.
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Repair Difficulty

Medium 3/5

Required Part

Indoor Humidity / Auxiliary Sensor
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