iComfort
iComfort Smart Thermostats Error Codes
Complete list of fault codes and troubleshooting guides. Use the search below to find your specific error.
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E0
Thermostat display shows E0 and will not connect to the home Wi‑Fi network
Wi‑Fi Radio Initialization Failure
E1
Thermostat displays E1 and shows indoor temperature as -- or extremely inaccurate
Indoor Temperature Sensor Open/Short
E10
Thermostat shows E10 and cannot connect to the iComfort cloud or mobile app.
Cloud Service / Server Communication Error
E11
Thermostat displays E11 and reports an incorrect system type or cannot control certain stages.
Configuration / Equipment Mismatch Error
E12
Thermostat shows E12 and reports a low battery or backup power fault (for models with battery backup).
Backup Power / Battery Fault
E13
Thermostat displays E13, and the system cycles off unexpectedly due to a safety lockout.
Safety Lockout / Excessive Fault Retries
E14
Thermostat shows E14 and reports an internal memory or firmware error.
Non‑Volatile Memory / Firmware Corruption
E15
Thermostat displays E15 and reports a sensor calibration error.
Sensor Calibration Out of Range
E16
Thermostat shows E16 and reports a remote sensor fault (for models with remote room sensors).
Remote Room Sensor Open/Short
E17
Thermostat displays E17 and reports that the equipment interface module is not detected.
Equipment Interface Module Communication Failure
E18
Thermostat shows E18 and reports a dehumidification sensor or control error.
Dehumidification Control Fault
E19
Thermostat displays E19 and reports Wi-Fi security or authentication error.
Wi-Fi Authentication Failure
E2
Thermostat shows E2 and humidity reading is missing or stuck at 0%/100%
Indoor Humidity Sensor Failure
E20
Thermostat shows E20 and reports a schedule or clock synchronization error.
Time/Date Synchronization Fault
E3
Thermostat displays E3 and outdoor temperature shows -- or is clearly wrong
Outdoor Temperature Sensor Open/Short
E4
Thermostat shows E4 and cannot detect the outdoor unit or communicating furnace/air handler
Communication Bus Failure with Outdoor/Indoor Unit
E5
Thermostat displays E5 and system will not energize heating or cooling stages
Low Voltage Power Supply Fault
E6
Thermostat shows E6 and will not control dehumidification or humidification functions
Accessory Control Output Fault
E7
Thermostat displays E7 and fan will not respond to commands or runs continuously
Indoor Fan Control Output Fault
E8
Thermostat shows E8 and system reports over‑temperature or overheated control
Thermostat Internal Over‑Temperature Fault
E9
Thermostat displays E9, and the touchscreen is unresponsive or erratic.
Touchscreen Interface Failure
Symptom
The thermostat backlight or display is very dim and hard to read.
Display Backlight Degradation
Symptom
The thermostat does not detect or control the whole-home dehumidifier.
Dehumidifier Control Failure
Symptom
The thermostat does not detect or control the whole-home humidifier.
Humidifier Control Failure
Symptom
The thermostat does not respond to mobile app commands even though it shows as online.
Cloud/App Control Latency or Desynchronization
Symptom
The thermostat emits a burning smell or feels unusually hot to the touch.
Overheating Electronics/Potential Short
Symptom
The thermostat fails to detect outdoor temperature even though an outdoor sensor is installed.
Outdoor Sensor Detection Failure
Symptom
The thermostat fan runs continuously even when the system is not heating or cooling.
Continuous Fan Operation
Symptom
The thermostat frequently reboots or restarts on its own.
Unstable Power or Internal Reset Fault
Symptom
The thermostat humidity reading is clearly wrong or does not change.
Indoor Humidity Sensing Issue
Symptom
The thermostat is on but will not turn on cooling when the temperature is set lower than the room temperature.
No Cool Call from Thermostat
Symptom
The thermostat is on but will not turn on heating when the temperature is set higher than the room temperature.
No Heat Call from Thermostat
Symptom
The thermostat is very slow to respond to touch or menu commands.
User Interface Performance Degradation
Symptom
The thermostat loses Wi-Fi connection intermittently but otherwise works.
Intermittent Wi-Fi Connectivity
Symptom
The thermostat shows random characters or garbled text on the display.
Display Data Corruption
Symptom
The thermostat temperature reading is consistently higher or lower than the actual room temperature.
Indoor Temperature Sensing / Placement Issue
Symptom
Thermostat cycles heating or cooling on and off too frequently (short cycling).
Improper Cycle Rate/Differential Settings
Symptom
Thermostat display is completely blank, and the system does not respond.
No Power to Thermostat
Symptom
Thermostat does not follow the programmed schedule and seems to change setpoints randomly.
Scheduling/Programming Misconfiguration
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| E0 |
Thermostat display shows E0 and will not connect to the home Wi‑Fi network
|
Wi‑Fi Radio Initialization Failure | View Details |
| E1 |
Thermostat displays E1 and shows indoor temperature as -- or extremely inaccurate
|
Indoor Temperature Sensor Open/Short | View Details |
| E10 |
Thermostat shows E10 and cannot connect to the iComfort cloud or mobile app.
|
Cloud Service / Server Communication Error | View Details |
| E11 |
Thermostat displays E11 and reports an incorrect system type or cannot control certain stages.
|
Configuration / Equipment Mismatch Error | View Details |
| E12 |
Thermostat shows E12 and reports a low battery or backup power fault (for models with battery backup).
|
Backup Power / Battery Fault | View Details |
| E13 |
Thermostat displays E13, and the system cycles off unexpectedly due to a safety lockout.
|
Safety Lockout / Excessive Fault Retries | View Details |
| E14 |
Thermostat shows E14 and reports an internal memory or firmware error.
|
Non‑Volatile Memory / Firmware Corruption | View Details |
| E15 |
Thermostat displays E15 and reports a sensor calibration error.
|
Sensor Calibration Out of Range | View Details |
| E16 |
Thermostat shows E16 and reports a remote sensor fault (for models with remote room sensors).
|
Remote Room Sensor Open/Short | View Details |
| E17 |
Thermostat displays E17 and reports that the equipment interface module is not detected.
|
Equipment Interface Module Communication Failure | View Details |
| E18 |
Thermostat shows E18 and reports a dehumidification sensor or control error.
|
Dehumidification Control Fault | View Details |
| E19 |
Thermostat displays E19 and reports Wi-Fi security or authentication error.
|
Wi-Fi Authentication Failure | View Details |
| E2 |
Thermostat shows E2 and humidity reading is missing or stuck at 0%/100%
|
Indoor Humidity Sensor Failure | View Details |
| E20 |
Thermostat shows E20 and reports a schedule or clock synchronization error.
|
Time/Date Synchronization Fault | View Details |
| E3 |
Thermostat displays E3 and outdoor temperature shows -- or is clearly wrong
|
Outdoor Temperature Sensor Open/Short | View Details |
| E4 |
Thermostat shows E4 and cannot detect the outdoor unit or communicating furnace/air handler
|
Communication Bus Failure with Outdoor/Indoor Unit | View Details |
| E5 |
Thermostat displays E5 and system will not energize heating or cooling stages
|
Low Voltage Power Supply Fault | View Details |
| E6 |
Thermostat shows E6 and will not control dehumidification or humidification functions
|
Accessory Control Output Fault | View Details |
| E7 |
Thermostat displays E7 and fan will not respond to commands or runs continuously
|
Indoor Fan Control Output Fault | View Details |
| E8 |
Thermostat shows E8 and system reports over‑temperature or overheated control
|
Thermostat Internal Over‑Temperature Fault | View Details |
| E9 |
Thermostat displays E9, and the touchscreen is unresponsive or erratic.
|
Touchscreen Interface Failure | View Details |
| – |
The thermostat backlight or display is very dim and hard to read.
|
Display Backlight Degradation | View Details |
| – |
The thermostat does not detect or control the whole-home dehumidifier.
|
Dehumidifier Control Failure | View Details |
| – |
The thermostat does not detect or control the whole-home humidifier.
|
Humidifier Control Failure | View Details |
| – |
The thermostat does not respond to mobile app commands even though it shows as online.
|
Cloud/App Control Latency or Desynchronization | View Details |
| – |
The thermostat emits a burning smell or feels unusually hot to the touch.
|
Overheating Electronics/Potential Short | View Details |
| – |
The thermostat fails to detect outdoor temperature even though an outdoor sensor is installed.
|
Outdoor Sensor Detection Failure | View Details |
| – |
The thermostat fan runs continuously even when the system is not heating or cooling.
|
Continuous Fan Operation | View Details |
| – |
The thermostat frequently reboots or restarts on its own.
|
Unstable Power or Internal Reset Fault | View Details |
| – |
The thermostat humidity reading is clearly wrong or does not change.
|
Indoor Humidity Sensing Issue | View Details |
| – |
The thermostat is on but will not turn on cooling when the temperature is set lower than the room temperature.
|
No Cool Call from Thermostat | View Details |
| – |
The thermostat is on but will not turn on heating when the temperature is set higher than the room temperature.
|
No Heat Call from Thermostat | View Details |
| – |
The thermostat is very slow to respond to touch or menu commands.
|
User Interface Performance Degradation | View Details |
| – |
The thermostat loses Wi-Fi connection intermittently but otherwise works.
|
Intermittent Wi-Fi Connectivity | View Details |
| – |
The thermostat shows random characters or garbled text on the display.
|
Display Data Corruption | View Details |
| – |
The thermostat temperature reading is consistently higher or lower than the actual room temperature.
|
Indoor Temperature Sensing / Placement Issue | View Details |
| – |
Thermostat cycles heating or cooling on and off too frequently (short cycling).
|
Improper Cycle Rate/Differential Settings | View Details |
| – |
Thermostat display is completely blank, and the system does not respond.
|
No Power to Thermostat | View Details |
| – |
Thermostat does not follow the programmed schedule and seems to change setpoints randomly.
|
Scheduling/Programming Misconfiguration | View Details |
No matching codes found
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