Unit stops and displays HL; compressor and fan shut down, control panel still responsive.

Safety first: Turn the unit OFF and unplug it before cleaning or opening any panels.

Step-by-step:

• 1. Power reset: Unplug the air conditioner for 10–15 minutes to allow the internal thermal protection to reset. Plug back in and test. If HL returns quickly, continue below.
• 2. Check placement and airflow: Ensure the unit is at least 12–16 inches away from walls or furniture at the rear and sides. De'Longhi portable units need clear airflow around the condenser intake and exhaust.
• 3. Clean rear air filter and grille: Remove the rear filter, wash with mild soap and warm water, dry completely, and reinstall. Use a vacuum with a brush attachment to clean dust from the rear grille and visible condenser fins (do not bend fins).
• 4. Inspect exhaust hose: Make sure the exhaust hose is not kinked, crushed, or longer than the recommended length. A restricted hose can cause high internal temperature and trigger HL.
• 5. Check for internal dust buildup (advanced): If comfortable, remove the rear panel (on portable models) to visually inspect the condenser coil and fan for heavy dust. Gently blow out dust with compressed air while keeping the fan blades from spinning. Reassemble carefully.
• 6. Sensor check (for technicians or advanced DIY): The condenser temperature sensor (NTC) may be out of range. If HL appears immediately on startup, the sensor may be open/shorted and should be tested with a multimeter and replaced if faulty.

Stop and call a technician if the unit smells of burning, the compressor is extremely hot to the touch, or HL appears instantly after power-on even in a cool room.