Place the unit on a level surface with at least 20–30 cm of space on all sides. Do not block the air inlet (usually at the back) or the outlet (usually at the top).
Keep windows and doors closed to prevent new humid air from entering.
Unplug the unit. Check the power cord for kinks. If the outlet voltage drops below 105V (common in older homes during summer), the top control board will underperform. Plug into a different circuit or install a voltage stabilizer.