Thermostat displays E3 and heating output is disabled or erratic; may occur on models with multiple sensors (room + floor).

Safety first: Turn off power to the thermostat and heating system before removing covers.

Steps to check:

• Reset to factory defaults: Enter the installer menu on the Salus thermostat (refer to the specific model manual) and perform a factory reset. This can clear incorrect sensor configuration that triggers E3.
• Check sensor selection: Ensure the thermostat is set to the correct sensor mode (e.g. room only, floor only, or room with floor limit). Using a floor sensor as a room sensor or vice versa can cause out-of-range readings.
• Verify ambient conditions: If the thermostat is installed in an extremely hot or cold area (e.g. boiler cupboard, unheated loft), relocate it to a suitable position within the specified operating temperature range.
• Power-cycle the system: Isolate power for 5 minutes, then restore. Observe if E3 reappears immediately or only under certain conditions (e.g. when heating starts).
• Check for wiring shorts: On models with external sensors, inspect the sensor cable for shorts to live/neutral or earth, which can corrupt readings.

Next steps: If E3 persists with correct configuration and environment, the internal measurement circuitry may be faulty. Replace the thermostat head or complete thermostat.