Condensation or visible moisture is present inside the Vaillant smart thermostat housing.

Safety: Switch off power to the thermostat circuit before removing the unit. Moisture and electricity are hazardous together.

• 1. Remove thermostat: Carefully remove the thermostat from its base and gently dry any visible moisture with a soft, dry cloth. Do not use heat guns or hairdryers.
• 2. Identify moisture source: Check for water leaks from pipes, roofs, or condensation on cold walls. Address the underlying building issue.
• 3. Improve location: If mounted on a cold external wall, consider relocating the thermostat to an internal wall to reduce condensation risk.
• 4. Allow to dry: Leave the thermostat in a dry, warm room (unpowered) for 24 hours before refitting.
• 5. Replace if damaged: If corrosion or malfunction persists after drying, replace the thermostat.