P2
Vaillant
Defrost Protection / Outdoor Coil Temperature Abnormal
P2 code, compressor stops during operation, especially in 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
Outdoor coil sensor reading out of range, Sensor not attached to coil, Heavy frost or ice buildup on outdoor coil, Defrost control malfunction on PCB
How to Fix / Troubleshooting
Safety: Isolate power before working on the outdoor unit.
- Inspect outdoor coil: Check for heavy frost or ice. If the coil is completely iced over, allow the unit to defrost by turning it off until ice melts.
- Clean coil: Remove dirt and debris from the coil to improve heat exchange.
- Check coil sensor: Locate the outdoor coil NTC sensor and ensure it is firmly attached to the coil. Reseat the connector on the PCB.
- Test sensor: Measure resistance and compare to the NTC chart. Replace if faulty.
- Test operation: Restore power and run in HEAT mode. If P2 recurs, the defrost algorithm or PCB may be faulty and should be checked by a Vaillant technician.
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Repair Difficulty
Medium
3/5
Required Part
Outdoor Coil NTC Temperature Sensor
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