De'Longhi dehumidifier stops and displays HL on the control panel; unit will not restart until unplugged and cooled.

Safety first: Unplug the dehumidifier and let it cool for at least 30 minutes before working on it. Do not operate the unit with panels removed.

Step-by-step:

• 1. Check room conditions: Ensure the unit is not placed in a very hot, confined space (e.g., small closet, near radiator, or in direct sunlight). De'Longhi dehumidifiers are typically rated for operation up to about 32–35°C. Move the unit to a cooler, well-ventilated area.
• 2. Clean the air filter: Remove the front or rear grille (depending on model) and slide out the dust filter. Vacuum off dust, then wash with lukewarm water and mild detergent. Allow it to dry completely before reinstalling.
• 3. Inspect air inlets/outlets: Make sure there is at least 20–30 cm clearance around all sides of the unit. Remove any curtains, furniture, or objects blocking airflow.
• 4. Check for heavy dust buildup: With the unit unplugged, use a flashlight to look through the grille at the evaporator and condenser coils. If they are heavily clogged with dust, gently vacuum with a soft brush attachment. Do not bend the fins.
• 5. Reset the unit: After cleaning and cooling, plug the unit back in and power it on. If HL clears and does not return, monitor operation for 30–60 minutes.
• 6. Suspect sensor or control fault: If HL reappears quickly in a normal-temperature room with clean filters, the ambient temperature sensor (NTC) or main control board may be faulty. At this point, replacement of the sensor or PCB is recommended by a qualified technician.

Do not bypass safety devices or operate the unit if it smells hot or shows signs of overheating.