Thermostat display shows E2 and heating cycles erratically

Safety first: Switch off power to the thermostat at the breaker before opening the wall unit.

Steps to troubleshoot E2 (floor sensor short):

• 1. Inspect sensor terminations:
  • Remove the Fibaro thermostat from its backplate.
  • Locate the SENSOR/NTC terminals.
  • Ensure the two sensor wires are not frayed or touching each other outside the terminal block.
• 2. Check for moisture damage:
  • If the sensor is installed in a bathroom or wet area, moisture may have entered the sensor probe or junction box.
  • Look for condensation, corrosion, or water traces in the wall box.
• 3. Measure resistance:
  • Disconnect the sensor wires from the thermostat.
  • Use a multimeter on resistance (Ω) across the two sensor wires.
  • A reading close to 0 Ω indicates a short circuit. Normal NTC sensors should be several kΩ.
• 4. Inspect cable path if accessible:
  • Check any accessible sections of the sensor cable (e.g., under floor access, junction boxes) for crushed or stapled areas.
  • Repair or replace damaged cable sections if possible.
• 5. Replace the sensor:
  • If the sensor is confirmed shorted, install a new compatible Fibaro floor sensor.
  • Route it in a protective conduit to prevent future damage and moisture ingress.
  • Reconnect to the thermostat and secure terminals.

When to call a professional: If the sensor cable is embedded in concrete or tiles and cannot be accessed, a professional may need to reconfigure the system to use air temperature control only or install a new sensor in a different location.