E4
AEG
Indoor/Outdoor Communication Error
Unit stops and displays E4; may occur during heating or defrost cycles.
Advertisements
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.
Advertisements
Possible Causes
Loose communication wiring between indoor and outdoor units, Reversed polarity on S1/S2 terminals, Electrical noise or poor earth, Faulty indoor or outdoor PCB communication circuit
How to Fix / Troubleshooting
Safety: Isolate power to both indoor and outdoor units before touching any wiring.
- Check power supply: Confirm correct voltage at the supply and that the breaker has not tripped. Restore if necessary.
- Inspect communication cable: At both indoor and outdoor terminals, verify that the communication wires (often marked S1/S2 or 1/2/3) are firmly clamped and not corroded.
- Verify polarity: Ensure the same wire colours are connected to the same terminal numbers on both indoor and outdoor units. Reversed polarity can cause E4.
- Check for damage: Follow the cable run where visible. Look for crushed, cut, or water-damaged sections. Repair or replace damaged cable with equivalent shielded cable if specified by AEG.
- Power cycle: After correcting wiring, turn power off for 10 minutes, then restore and test operation.
- If E4 remains: One of the PCBs may have a failed communication circuit. This requires professional diagnosis with AEG service tools.
Advertisements
Repair Difficulty
Hard
4/5
Required Part
Indoor-Outdoor Communication Harness
Check Price on Amazon
We may earn a commission from links on this page.
Advertisements