P4
AEG Indoor Coil High Temperature Protection (Cooling) or Low Temperature Protection (Heating) – Model-dependent

P4 displayed; unit may stop and restart after some time.

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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

Blocked air filters, Indoor fan failure, Low refrigerant charge, Blocked expansion device, Incorrect temperature sensor reading

How to Fix / Troubleshooting

Safety: Turn off power before cleaning or opening the unit.

  • Clean filters: Remove and wash the indoor air filters with mild detergent. Dry completely before reinstalling.
  • Check indoor fan: Ensure the fan runs at all selected speeds. If airflow is weak or intermittent, see indoor fan diagnostics.
  • Inspect coil: Look for heavy dust or ice on the evaporator coil. Clean gently and allow ice to melt fully.
  • Reset and test: After cleaning and drying, power the unit back on and test. If P4 recurs, a refrigerant or sensor issue is likely.
  • Technician required: Have an AEG technician check refrigerant charge and coil sensor operation.
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Repair Difficulty

Medium 3/5

Required Part

Evaporator Temperature Sensor (NTC)
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