P5
Mitsubishi Electric
Outdoor Coil Temperature Sensor / Defrost Control Error
System stops with P5, often during heating mode
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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
Faulty outdoor coil thermistor, Thermistor not attached to coil, Damaged thermistor wiring, Outdoor PCB sensor circuit fault
How to Fix / Troubleshooting
Safety first: Turn off power at the outdoor disconnect before opening the unit.
Steps:
- Locate coil thermistor: Find the thermistor clipped to the outdoor heat exchanger coil.
- Check attachment: Ensure the sensor is firmly clipped to the coil and properly insulated if required.
- Inspect wiring: Look for cuts, corrosion, or rodent damage along the thermistor wires. Repair or replace as needed.
- Measure resistance: With power OFF, disconnect the thermistor and measure resistance. Compare to Mitsubishi Electric’s temperature–resistance chart. Replace if out of range.
- PCB check: If a new thermistor does not resolve P5, the outdoor PCB may be faulty and should be replaced by a technician.
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Repair Difficulty
Medium
3/5
Required Part
Outdoor Coil Thermistor
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