Thermostat display shows E2 and room temperature reading is incorrect or dashes

Safety: Turn off the circuit breaker feeding the thermostat before removing it from the wall. Confirm power is off.

Steps to troubleshoot E2 (sensor short):

• 1. Inspect environment: Check for excessive humidity, water leaks, or condensation near the thermostat. Dry the area and ensure the thermostat is not installed directly above a humidifier or in a bathroom without ventilation.
• 2. Remove thermostat from wall: Gently pull the Stelpro smart thermostat off its wall plate. Inspect the back of the unit and the wall opening for moisture, corrosion, or debris.
• 3. Visual inspection of sensor area: Locate the small thermistor (NTC) on the PCB near the air vents. Look for signs of corrosion, burnt spots, or foreign material bridging the sensor leads.
• 4. Clean the PCB: If you see dust or debris, use compressed air or a soft brush to clean the board. Do not use water. For light corrosion, a small amount of electronics contact cleaner on a cotton swab can be used carefully.
• 5. Measure sensor resistance: With power OFF, use a multimeter to measure resistance across the sensor pads. A reading near 0 ohms indicates a short. Compare to expected NTC value at room temperature (often around 10kΩ). If shorted, the sensor or board is defective.
• 6. Check for solder bridges: Under good lighting, inspect the solder joints around the sensor. If two pads are bridged by solder, the sensor will read short. This typically requires rework by a technician.
• 7. Replace thermostat: If the sensor is shorted internally or the PCB is damaged, replace the entire Stelpro smart thermostat with the same or updated compatible model.

Note: Do not attempt to scrape or cut PCB traces unless you are an experienced electronics technician. For most homeowners, replacement is the safest option.