Indoor unit stops and displays E1; cooling or heating stops shortly after startup.

Safety first: Turn off the AEG air conditioner at the mains isolator or circuit breaker and unplug it if it has a plug. Wait at least 5 minutes before removing any covers.

Steps to check and correct:

• Power reset: Turn power off for 5–10 minutes, then restore power and try operating in COOL mode. If E1 returns, continue below.
• Access indoor PCB: Remove the front fascia and filter of the indoor unit. Remove the small PCB cover (usually on the right-hand side).
• Locate room sensor: Find the small NTC sensor (usually in front of the evaporator coil or in the air intake) connected by two thin wires to the indoor PCB.
• Check connections: Ensure the sensor plug is fully seated on the PCB and that the wires are not cut, pinched, or corroded. Reseat the connector.
• Visual inspection: Look for signs of moisture damage or burnt components around the sensor connector on the PCB.
• If you have a multimeter: Disconnect the sensor and measure its resistance at room temperature (typically 5–20 kΩ depending on model). If it reads open (infinite) or near 0 Ω, the sensor is faulty.
• Replace if faulty: Order a compatible AEG indoor room temperature sensor (NTC) using the full model number of your unit. Install it in the same position and route the cable as originally.
• If sensor is OK but E1 persists: The indoor control PCB sensor circuit may be defective. This is a board-level repair and should be handled by a qualified technician.