P4
Mitsubishi Electric
Compressor Discharge Temperature High
System stops with P4, often associated with compressor temperature issues
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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
Low refrigerant charge, Blocked outdoor coil, Non-condensable gases in system, Faulty discharge pipe thermistor
How to Fix / Troubleshooting
Safety first: Refrigerant circuit work must be done by certified personnel. Turn off power before inspection.
Steps:
- Clean coils and filters: Ensure both indoor and outdoor heat exchangers are clean and unobstructed to reduce discharge temperature.
- Check airflow: Verify indoor fan and outdoor fan are operating correctly and that vents are not blocked.
- Inspect discharge thermistor: Locate the discharge pipe thermistor on the compressor outlet line. Ensure it is firmly attached and insulated. Replace if damaged or reading incorrectly.
- Refrigerant diagnosis (technician): A technician should check operating pressures, superheat, and subcooling to determine if the system is undercharged, overcharged, or contaminated, and then recover, evacuate, and recharge as needed.
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Repair Difficulty
Professional Required
5/5
Required Part
Compressor Discharge Pipe Thermistor
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