E1
TP-Link Kasa
Room Temperature Sensor Failure
Thermostat shows E1 and HVAC system does not respond to temperature changes
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Failed onboard thermistor, Damaged sensor trace on PCB, Moisture ingress into thermostat housing, Manufacturing defect in sensor circuit
How to Fix / Troubleshooting
Safety: Switch off power to the furnace/air handler at the breaker before removing the thermostat from the wall plate.
- Visual inspection: Remove the thermostat from its wall plate. Check for signs of condensation, corrosion, or liquid damage on the sensor area (usually near the bottom or side vents).
- Stabilize environment: If the thermostat is in a very humid area (bathroom, kitchen), improve ventilation or relocate the thermostat to a drier interior wall if possible.
- Power cycle and reset: Turn power off for 1 minute, then on. If E1 remains, perform a factory reset via the Kasa app and reconfigure.
- Check temperature reading: Compare the thermostat’s displayed temperature (if available) to a known-good thermometer. If it is wildly inaccurate or not displayed at all, the sensor is likely failed.
- Resolution: The internal temperature sensor is not field-replaceable on most Kasa thermostats. Replace the thermostat unit.
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Repair Difficulty
Medium
3/5
Required Part
Internal Thermistor / Temperature Sensor Assembly
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