Wiser Room Thermostat displays E04 and cannot control the heating; app shows sensor fault.

Safety: No mains work is required. Do not open the thermostat casing beyond the battery cover.

• Restart the thermostat: Remove and reinsert batteries as per the user manual to force a reboot.
• Relocate if in damp area: If the thermostat is installed in a bathroom, kitchen, or other high-humidity area, relocate it to a drier location. Persistent condensation can damage sensors.
• Check app configuration: In the Wiser app, ensure the thermostat is correctly assigned to a room and that no unsupported external sensor options are enabled.

If E04 persists after reboot and relocation, the internal sensor circuitry is faulty. Replace the Wiser Room Thermostat.