Analysis by Lukas & Team
Troubleshoot an Ecobee SmartSensor reporting 99°C and a short circuit error. Diagnostics and solutions for Canadian homes.
Lukas leads the technical research department at Digital Home Faults. Together with a team of systems analysts, he specializes in translating complex manufacturer error codes into actionable diagnostic steps for the Canadian market.
The Ecobee app displays the battery level of connected SmartSensors. Navigate to the sensor's settings within the app to view the battery status.
The Ecobee SmartSensor uses a CR2477 3V lithium coin cell battery.
Open the Ecobee app, navigate to the thermostat settings, and select 'Add a Sensor'. Follow the on-screen instructions to re-pair the SmartSensor. You may need to press and hold the sensor button to initiate pairing.
Do not attempt to disassemble or repair the SmartSensor beyond battery replacement and cleaning. Internal components may be damaged, and improper handling could create a safety hazard. SmartSensors do not directly control high-voltage circuits.
Sensor displays 99°C (210°F) or a similar abnormally high temperature. The Ecobee thermostat may report a 'Short Circuit' error associated with the affected SmartSensor. No LED activity or a flashing red LED may be observed on the sensor. App-side error logs confirm sensor malfunction.
If you suspect Zigbee interference, try relocating the Ecobee thermostat or the SmartSensor slightly. Experiment with different mounting locations to optimize signal strength. A Zigbee channel scan might identify less congested frequencies.
Ecobee SmartSensors use NTC (Negative Temperature Coefficient) thermistors to measure temperature. These thermistors exhibit a decrease in resistance as temperature increases. A short circuit across the thermistor or its associated wiring results in a near-zero resistance reading, misinterpreted as a very high temperature (99°C). Zigbee radio communicates the data to the thermostat.