Thermostat displays E1 and cannot control heating; room temperature reading is obviously wrong or shows dashes/--

Safety first: Turn off power to the thermostat at the circuit breaker or boiler/HVAC service switch before removing it from the wall. Confirm power is off with a non-contact voltage tester.

Steps to troubleshoot:

• Remove the thermostat from its wall plate or open the front cover (depending on model).
• Locate the internal room temperature sensor (usually a small NTC thermistor near the bottom air vent on the main PCB).
• Inspect the sensor and its solder joints for cracks, corrosion, or broken leads.
• Gently reseat any small plug-in sensor connector if present.
• With power still OFF, measure resistance across the NTC sensor with a multimeter; compare to Tuya’s temperature–resistance chart (e.g., ~10kΩ at 25°C for common NTCs). Infinite resistance indicates open sensor; near 0Ω indicates shorted sensor.
• If the sensor is defective or physically damaged, replace the thermostat main board or the NTC sensor module if it is a separate, replaceable part.
• Reassemble the thermostat, restore power, and verify that the E1 code clears and the temperature reading is realistic.

When to call a professional: If you are not comfortable opening the thermostat or soldering a new sensor onto the PCB, contact a qualified HVAC or electronics technician.