E6 error and thermostat indicates internal humidity sensor fault (on models with humidity control).

Safety: Disconnect power before opening the thermostat housing.

• Step 1 – Clean sensor area:
  • Open the thermostat front cover.
  • Locate the humidity sensor (small vented component).
  • Gently blow away dust with dry compressed air.
  • Do not use liquids or solvents.
• Step 2 – Dry out condensation:
  • If the thermostat is in a very humid area, allow it to dry with power off for several hours.
• Step 3 – Reset device:
  • Reassemble, restore power, and check if E6 clears.
• Step 4 – Disable humidity control (workaround):
  • In settings, disable humidity-based control if available.
• Step 5 – Replace thermostat if sensor is defective:
  • Humidity sensor is usually integrated and not user-replaceable.
  • Replace the Protherm smart thermostat if humidity measurement is required.