F4
AEG Discharge Pipe Temperature Sensor Fault

F4 error; unit may stop with no cooling or heating, often after running for 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

Failed compressor discharge NTC sensor, Sensor detached from discharge pipe, Damaged sensor insulation, Faulty outdoor PCB sensor input

How to Fix / Troubleshooting

Safety: The discharge pipe can be extremely hot. Ensure power is off and the system has cooled before touching any pipes.

  • Locate sensor: Find the sensor clipped or strapped to the small-diameter copper pipe leaving the compressor (discharge line).
  • Check attachment and insulation: Ensure the sensor is firmly attached and covered with insulation tape or foam as originally. Re-secure if loose.
  • Inspect cable: Look for heat damage or brittle insulation near the compressor.
  • Test sensor: Measure resistance with a multimeter. Replace with a correct AEG discharge temperature sensor if readings are abnormal.
  • If F4 persists: The outdoor PCB may misread the sensor and require replacement by a technician.
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Repair Difficulty

Hard 4/5

Required Part

Discharge Pipe Temperature Sensor (NTC)
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