Geo
Geo 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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E01
Thermostat display shows E01 and will not connect to Wi‑Fi or the Geo mobile app.
Wi‑Fi Radio Communication Failure
E02
Thermostat displays E02 and does not detect the C (common) wire; screen may dim or reboot when calling for heat or cool.
C‑Wire Power Loss / Low Voltage Supply
E03
Thermostat shows E03 and will not control heating; system remains off even when heat is requested.
W (Heat Call) Circuit Open or Short
E04
Thermostat displays E04 and cooling will not start; AC condenser does not engage when cool is requested.
Y (Cool Call) Circuit Open or Short
E05
Thermostat shows E05 and fan will not run in Auto or On mode.
G (Fan) Circuit Failure
E06
Thermostat displays E06 and shows incorrect room temperature (far off from actual) or fluctuating rapidly.
Internal Temperature Sensor Fault
E07
Thermostat shows E07 and humidity readings are missing or clearly wrong (0% or 99% constantly).
Internal Humidity Sensor Failure
E08
Thermostat displays E08 and loses power intermittently, rebooting when the system starts.
Power Draw / Load Shedding Error
E09
Thermostat shows E09 and cannot detect the heating/cooling system type during setup.
System Configuration / Equipment Detection Error
E10
Thermostat displays E10 and indicates an external sensor fault; remote room sensor readings are missing.
Remote Room Sensor Communication Failure
E11
Thermostat shows E11 and indicates an outdoor temperature sensor fault; outdoor readings are blank or frozen.
Outdoor Sensor Failure
E12
Thermostat displays E12 and cannot complete firmware update; device may reboot repeatedly.
Firmware Update / Flash Memory Error
E13
Thermostat shows E13 and cannot connect to the Geo cloud service; remote control via app fails while local control works.
Cloud Service / TLS Handshake Error
E14
Thermostat displays E14 and indicates an internal battery or backup power fault; settings may reset after power loss.
Backup Power / Supercapacitor Failure
E15
Thermostat shows E15 and reports an internal temperature overheat condition; device may shut down temporarily.
Thermostat Over‑Temperature Protection
E16
Thermostat displays E16 and indicates a short circuit on one of the control outputs; HVAC system may be locked out.
Control Output Short Circuit Protection
E17
Thermostat shows E17 and indicates a low‑temperature freeze protection alert; heating may be forced on or system locked out.
Freeze Protection / Low Ambient Lockout
E18
Thermostat displays E18 and indicates a dehumidifier or humidifier accessory fault.
Accessory Control Circuit Error
E19
Thermostat shows E19 and indicates an internal clock or timekeeping error; schedules may not run correctly.
Real‑Time Clock (RTC) Failure
E20
Thermostat displays E20 and indicates a sensor calibration or configuration mismatch after a firmware update.
Sensor Calibration Data Corruption
Symptom
Thermostat backlight is very dim or flickers, but the display content is still visible.
Backlight LED Driver Degradation
Symptom
Thermostat calls for cooling but the outdoor AC unit does not start; indoor blower may run.
Cool Call Not Activating Condenser
Symptom
Thermostat calls for heat but the furnace does not start; no error code is shown on the thermostat.
Heat Call Not Activating Furnace
Symptom
Thermostat display is on but touch screen is unresponsive or only responds intermittently.
Capacitive Touch Panel Failure
Symptom
Thermostat does not detect or use the connected remote room sensor; readings only show internal sensor.
Remote Sensor Not Recognized
Symptom
Thermostat does not enter Emergency Heat mode when selected on a heat pump system.
Emergency Heat Command Not Engaging
Symptom
Thermostat does not follow programmed schedule; temperature holds at one setting or changes at wrong times.
Scheduling / Program Logic Fault
Symptom
Thermostat does not respond to commands from the Geo mobile app, even though it appears online.
Cloud Command Processing / API Desynchronization
Symptom
Thermostat does not turn on the fan in 'Fan On' mode, but fan runs during heating or cooling.
Manual Fan (G) Control Failure
Symptom
Thermostat fails to dehumidify using the connected whole‑home dehumidifier or AC overcool feature.
Dehumidification Control Not Operating
Symptom
Thermostat fails to power the connected whole‑home humidifier when humidity is low and a call is expected.
Humidifier Control Output Not Activating
Symptom
Thermostat frequently cycles the HVAC system on and off in short bursts (short cycling).
Short Cycling Due to Control Settings or Sensor Placement
Symptom
Thermostat frequently disconnects from Wi‑Fi and drops offline in the Geo app, but local control still works.
Intermittent Wi‑Fi Connectivity
Symptom
Thermostat is set to Cool but the air from vents is warm or not sufficiently cool.
Improper Cooling Operation / Mode Misconfiguration
Symptom
Thermostat is set to Heat but the air coming from vents is cool or cold.
Reversing Valve or Mode Configuration Error
Symptom
Thermostat plastic housing feels unusually warm to the touch during normal operation.
Elevated Internal Operating Temperature
Symptom
Thermostat reboots randomly several times a day without user interaction.
Unstable Internal Power or Firmware Crash
Symptom
Thermostat screen is completely blank and unresponsive; HVAC system does not respond to temperature changes.
No Power to Thermostat
Symptom
Thermostat shows 'Aux Heat' or 'Emergency Heat' running too often on a heat pump system, increasing energy use.
Auxiliary Heat Overuse
Symptom
Thermostat shows humidity readings that are clearly inaccurate compared to other hygrometers.
Humidity Reading Calibration Error
Symptom
Thermostat shows large temperature swings; room becomes too hot or too cold before system turns on or off.
Improper Cycle Rate / Differential Settings
Symptom
Thermostat shows outdoor temperature even though no outdoor sensor is installed, and the value is clearly wrong.
Phantom Outdoor Sensor Reading
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| E01 |
Thermostat display shows E01 and will not connect to Wi‑Fi or the Geo mobile app.
|
Wi‑Fi Radio Communication Failure | View Details |
| E02 |
Thermostat displays E02 and does not detect the C (common) wire; screen may dim or reboot when calling for heat or cool.
|
C‑Wire Power Loss / Low Voltage Supply | View Details |
| E03 |
Thermostat shows E03 and will not control heating; system remains off even when heat is requested.
|
W (Heat Call) Circuit Open or Short | View Details |
| E04 |
Thermostat displays E04 and cooling will not start; AC condenser does not engage when cool is requested.
|
Y (Cool Call) Circuit Open or Short | View Details |
| E05 |
Thermostat shows E05 and fan will not run in Auto or On mode.
|
G (Fan) Circuit Failure | View Details |
| E06 |
Thermostat displays E06 and shows incorrect room temperature (far off from actual) or fluctuating rapidly.
|
Internal Temperature Sensor Fault | View Details |
| E07 |
Thermostat shows E07 and humidity readings are missing or clearly wrong (0% or 99% constantly).
|
Internal Humidity Sensor Failure | View Details |
| E08 |
Thermostat displays E08 and loses power intermittently, rebooting when the system starts.
|
Power Draw / Load Shedding Error | View Details |
| E09 |
Thermostat shows E09 and cannot detect the heating/cooling system type during setup.
|
System Configuration / Equipment Detection Error | View Details |
| E10 |
Thermostat displays E10 and indicates an external sensor fault; remote room sensor readings are missing.
|
Remote Room Sensor Communication Failure | View Details |
| E11 |
Thermostat shows E11 and indicates an outdoor temperature sensor fault; outdoor readings are blank or frozen.
|
Outdoor Sensor Failure | View Details |
| E12 |
Thermostat displays E12 and cannot complete firmware update; device may reboot repeatedly.
|
Firmware Update / Flash Memory Error | View Details |
| E13 |
Thermostat shows E13 and cannot connect to the Geo cloud service; remote control via app fails while local control works.
|
Cloud Service / TLS Handshake Error | View Details |
| E14 |
Thermostat displays E14 and indicates an internal battery or backup power fault; settings may reset after power loss.
|
Backup Power / Supercapacitor Failure | View Details |
| E15 |
Thermostat shows E15 and reports an internal temperature overheat condition; device may shut down temporarily.
|
Thermostat Over‑Temperature Protection | View Details |
| E16 |
Thermostat displays E16 and indicates a short circuit on one of the control outputs; HVAC system may be locked out.
|
Control Output Short Circuit Protection | View Details |
| E17 |
Thermostat shows E17 and indicates a low‑temperature freeze protection alert; heating may be forced on or system locked out.
|
Freeze Protection / Low Ambient Lockout | View Details |
| E18 |
Thermostat displays E18 and indicates a dehumidifier or humidifier accessory fault.
|
Accessory Control Circuit Error | View Details |
| E19 |
Thermostat shows E19 and indicates an internal clock or timekeeping error; schedules may not run correctly.
|
Real‑Time Clock (RTC) Failure | View Details |
| E20 |
Thermostat displays E20 and indicates a sensor calibration or configuration mismatch after a firmware update.
|
Sensor Calibration Data Corruption | View Details |
| – |
Thermostat backlight is very dim or flickers, but the display content is still visible.
|
Backlight LED Driver Degradation | View Details |
| – |
Thermostat calls for cooling but the outdoor AC unit does not start; indoor blower may run.
|
Cool Call Not Activating Condenser | View Details |
| – |
Thermostat calls for heat but the furnace does not start; no error code is shown on the thermostat.
|
Heat Call Not Activating Furnace | View Details |
| – |
Thermostat display is on but touch screen is unresponsive or only responds intermittently.
|
Capacitive Touch Panel Failure | View Details |
| – |
Thermostat does not detect or use the connected remote room sensor; readings only show internal sensor.
|
Remote Sensor Not Recognized | View Details |
| – |
Thermostat does not enter Emergency Heat mode when selected on a heat pump system.
|
Emergency Heat Command Not Engaging | View Details |
| – |
Thermostat does not follow programmed schedule; temperature holds at one setting or changes at wrong times.
|
Scheduling / Program Logic Fault | View Details |
| – |
Thermostat does not respond to commands from the Geo mobile app, even though it appears online.
|
Cloud Command Processing / API Desynchronization | View Details |
| – |
Thermostat does not turn on the fan in 'Fan On' mode, but fan runs during heating or cooling.
|
Manual Fan (G) Control Failure | View Details |
| – |
Thermostat fails to dehumidify using the connected whole‑home dehumidifier or AC overcool feature.
|
Dehumidification Control Not Operating | View Details |
| – |
Thermostat fails to power the connected whole‑home humidifier when humidity is low and a call is expected.
|
Humidifier Control Output Not Activating | View Details |
| – |
Thermostat frequently cycles the HVAC system on and off in short bursts (short cycling).
|
Short Cycling Due to Control Settings or Sensor Placement | View Details |
| – |
Thermostat frequently disconnects from Wi‑Fi and drops offline in the Geo app, but local control still works.
|
Intermittent Wi‑Fi Connectivity | View Details |
| – |
Thermostat is set to Cool but the air from vents is warm or not sufficiently cool.
|
Improper Cooling Operation / Mode Misconfiguration | View Details |
| – |
Thermostat is set to Heat but the air coming from vents is cool or cold.
|
Reversing Valve or Mode Configuration Error | View Details |
| – |
Thermostat plastic housing feels unusually warm to the touch during normal operation.
|
Elevated Internal Operating Temperature | View Details |
| – |
Thermostat reboots randomly several times a day without user interaction.
|
Unstable Internal Power or Firmware Crash | View Details |
| – |
Thermostat screen is completely blank and unresponsive; HVAC system does not respond to temperature changes.
|
No Power to Thermostat | View Details |
| – |
Thermostat shows 'Aux Heat' or 'Emergency Heat' running too often on a heat pump system, increasing energy use.
|
Auxiliary Heat Overuse | View Details |
| – |
Thermostat shows humidity readings that are clearly inaccurate compared to other hygrometers.
|
Humidity Reading Calibration Error | View Details |
| – |
Thermostat shows large temperature swings; room becomes too hot or too cold before system turns on or off.
|
Improper Cycle Rate / Differential Settings | View Details |
| – |
Thermostat shows outdoor temperature even though no outdoor sensor is installed, and the value is clearly wrong.
|
Phantom Outdoor Sensor Reading | View Details |
No matching codes found
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