GLAS
GLAS 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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C001
Thermostat displays C001 and cannot connect to Wi‑Fi network; cloud features and remote app control unavailable.
Wi‑Fi Radio or Network Authentication Fault
C002
Thermostat shows C002 and cannot reach the GLAS cloud service; local control works but mobile app and voice assistant integration fail.
Cloud Service Communication Failure
C003
Thermostat displays C003 and voice assistant integration (e.g., Cortana/Alexa/Google) fails to respond or link.
Voice Service Integration Error
C010
Thermostat shows C010 and screen becomes sluggish or unresponsive; some features may be disabled.
Firmware or Operating System Corruption
D001
Thermostat displays D001 and will not activate the dehumidifier or over‑cooling function when humidity is high.
Dehumidification Control Output Fault
G001
Thermostat shows G001 and the indoor blower fan does not run when heating or cooling is active.
Open G (Fan) Circuit
G002
Thermostat displays G002 and the indoor blower fan runs continuously even when GLAS is set to Auto and no heating or cooling is active.
Shorted G (Fan) Circuit
H001
Thermostat displays H001 and will not activate the humidifier when humidity is low.
Humidifier Control Output Fault
O/B01
Thermostat shows O/B01 and heat pump reversing valve does not switch correctly; system may cool when calling for heat or heat when calling for cool.
Reversing Valve Control Fault (O/B Terminal)
P001
Thermostat displays P001 and will not power on fully or reboots repeatedly; screen may flicker or stay dark.
Insufficient 24 VAC Power or C‑Wire Fault
P002
Thermostat shows P002 and reports low power; display may dim or shut off when calling for heat or cool.
Low Voltage Under Load
P010
Thermostat displays P010 and reports internal temperature sensor error; room temperature reading is blank or shows dashes.
Onboard Temperature Sensor Failure
P011
Thermostat shows P011 and humidity reading is missing or stuck at 0% or 100%.
Onboard Humidity Sensor Failure
P012
Thermostat displays P012 and VOC/air quality readings are unavailable or clearly incorrect.
VOC / Air Quality Sensor Failure
P020
Thermostat shows P020 and the touchscreen does not respond to taps or swipes, or responds intermittently.
Capacitive Touchscreen Failure
P030
Thermostat displays P030 and motion/occupancy detection does not work; GLAS does not switch between occupied and unoccupied modes.
Occupancy / Proximity Sensor Failure
S001
Thermostat displays S001 and cannot detect the type of HVAC system connected; setup wizard cannot complete.
System Detection / Configuration Error
S002
Thermostat shows S002 and reports an internal sensor calibration error; temperature or humidity readings are clearly off by a large margin.
Sensor Calibration Fault
W001
Thermostat shows W001 and will not activate the heating system when heat is demanded.
Open W (Heat Call) Circuit
W002
Thermostat displays W002 and the heating system runs continuously or cycles unexpectedly even when GLAS is not calling for heat.
Shorted W (Heat Call) Circuit
Y001
Thermostat shows Y001 and will not start the air conditioner when cooling is demanded.
Open Y (Cool Call) Circuit
Y002
Thermostat displays Y002 and the air conditioner runs when GLAS is not calling for cooling, or continues running after setpoint is reached.
Shorted Y (Cool Call) Circuit
Symptom
Thermostat and HVAC system short cycle: heating or cooling turns on and off rapidly in short bursts.
Short Cycling Control or Sensing Issue
Symptom
Thermostat becomes very warm to the touch and may behave erratically.
Overheating of Thermostat Electronics
Symptom
Thermostat calls for cooling but the outdoor AC unit does not start; indoor blower may run.
Cool Call Not Reaching Condenser
Symptom
Thermostat calls for heat but the furnace does not start; no error code is displayed on GLAS.
Heat Call Not Reaching Furnace
Symptom
Thermostat does not follow the programmed schedule; temperature setpoints change at the wrong times or not at all.
Scheduling / Timekeeping Fault
Symptom
Thermostat does not respond to touch or responds only intermittently; display is lit but cannot be controlled.
Touchscreen Input Failure
Symptom
Thermostat emits a buzzing or high‑pitched noise during operation.
Electrical Noise from Internal Components
Symptom
Thermostat frequently disconnects from Wi‑Fi and then reconnects; remote control via app is unreliable.
Unstable Wi‑Fi Connection
Symptom
Thermostat glass surface is frequently fogged or shows condensation.
Condensation on Thermostat Surface
Symptom
Thermostat powers on but frequently reboots or restarts by itself, especially when heating or cooling starts.
Intermittent Power Drop or Internal Overcurrent
Symptom
Thermostat screen is completely blank and does not power on at all.
No Power to Thermostat
Symptom
Thermostat shows humidity that is clearly incorrect (e.g., stuck at 10% or 90%) compared to other hygrometers.
Inaccurate Humidity Sensing
Symptom
Thermostat shows temperature that is clearly too high or too low compared to the actual room temperature.
Inaccurate Temperature Sensing
Symptom
Thermostat shows that the fan is off, but the indoor blower continues to run.
Fan Run‑On Not Controlled by Thermostat
Symptom
Thermostat will not connect to the mobile app or cannot be discovered during setup, even though Wi‑Fi is working.
App Pairing / Discovery Failure
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| C001 |
Thermostat displays C001 and cannot connect to Wi‑Fi network; cloud features and remote app control unavailable.
|
Wi‑Fi Radio or Network Authentication Fault | View Details |
| C002 |
Thermostat shows C002 and cannot reach the GLAS cloud service; local control works but mobile app and voice assistant integration fail.
|
Cloud Service Communication Failure | View Details |
| C003 |
Thermostat displays C003 and voice assistant integration (e.g., Cortana/Alexa/Google) fails to respond or link.
|
Voice Service Integration Error | View Details |
| C010 |
Thermostat shows C010 and screen becomes sluggish or unresponsive; some features may be disabled.
|
Firmware or Operating System Corruption | View Details |
| D001 |
Thermostat displays D001 and will not activate the dehumidifier or over‑cooling function when humidity is high.
|
Dehumidification Control Output Fault | View Details |
| G001 |
Thermostat shows G001 and the indoor blower fan does not run when heating or cooling is active.
|
Open G (Fan) Circuit | View Details |
| G002 |
Thermostat displays G002 and the indoor blower fan runs continuously even when GLAS is set to Auto and no heating or cooling is active.
|
Shorted G (Fan) Circuit | View Details |
| H001 |
Thermostat displays H001 and will not activate the humidifier when humidity is low.
|
Humidifier Control Output Fault | View Details |
| O/B01 |
Thermostat shows O/B01 and heat pump reversing valve does not switch correctly; system may cool when calling for heat or heat when calling for cool.
|
Reversing Valve Control Fault (O/B Terminal) | View Details |
| P001 |
Thermostat displays P001 and will not power on fully or reboots repeatedly; screen may flicker or stay dark.
|
Insufficient 24 VAC Power or C‑Wire Fault | View Details |
| P002 |
Thermostat shows P002 and reports low power; display may dim or shut off when calling for heat or cool.
|
Low Voltage Under Load | View Details |
| P010 |
Thermostat displays P010 and reports internal temperature sensor error; room temperature reading is blank or shows dashes.
|
Onboard Temperature Sensor Failure | View Details |
| P011 |
Thermostat shows P011 and humidity reading is missing or stuck at 0% or 100%.
|
Onboard Humidity Sensor Failure | View Details |
| P012 |
Thermostat displays P012 and VOC/air quality readings are unavailable or clearly incorrect.
|
VOC / Air Quality Sensor Failure | View Details |
| P020 |
Thermostat shows P020 and the touchscreen does not respond to taps or swipes, or responds intermittently.
|
Capacitive Touchscreen Failure | View Details |
| P030 |
Thermostat displays P030 and motion/occupancy detection does not work; GLAS does not switch between occupied and unoccupied modes.
|
Occupancy / Proximity Sensor Failure | View Details |
| S001 |
Thermostat displays S001 and cannot detect the type of HVAC system connected; setup wizard cannot complete.
|
System Detection / Configuration Error | View Details |
| S002 |
Thermostat shows S002 and reports an internal sensor calibration error; temperature or humidity readings are clearly off by a large margin.
|
Sensor Calibration Fault | View Details |
| W001 |
Thermostat shows W001 and will not activate the heating system when heat is demanded.
|
Open W (Heat Call) Circuit | View Details |
| W002 |
Thermostat displays W002 and the heating system runs continuously or cycles unexpectedly even when GLAS is not calling for heat.
|
Shorted W (Heat Call) Circuit | View Details |
| Y001 |
Thermostat shows Y001 and will not start the air conditioner when cooling is demanded.
|
Open Y (Cool Call) Circuit | View Details |
| Y002 |
Thermostat displays Y002 and the air conditioner runs when GLAS is not calling for cooling, or continues running after setpoint is reached.
|
Shorted Y (Cool Call) Circuit | View Details |
| – |
Thermostat and HVAC system short cycle: heating or cooling turns on and off rapidly in short bursts.
|
Short Cycling Control or Sensing Issue | View Details |
| – |
Thermostat becomes very warm to the touch and may behave erratically.
|
Overheating of Thermostat Electronics | View Details |
| – |
Thermostat calls for cooling but the outdoor AC unit does not start; indoor blower may run.
|
Cool Call Not Reaching Condenser | View Details |
| – |
Thermostat calls for heat but the furnace does not start; no error code is displayed on GLAS.
|
Heat Call Not Reaching Furnace | View Details |
| – |
Thermostat does not follow the programmed schedule; temperature setpoints change at the wrong times or not at all.
|
Scheduling / Timekeeping Fault | View Details |
| – |
Thermostat does not respond to touch or responds only intermittently; display is lit but cannot be controlled.
|
Touchscreen Input Failure | View Details |
| – |
Thermostat emits a buzzing or high‑pitched noise during operation.
|
Electrical Noise from Internal Components | View Details |
| – |
Thermostat frequently disconnects from Wi‑Fi and then reconnects; remote control via app is unreliable.
|
Unstable Wi‑Fi Connection | View Details |
| – |
Thermostat glass surface is frequently fogged or shows condensation.
|
Condensation on Thermostat Surface | View Details |
| – |
Thermostat powers on but frequently reboots or restarts by itself, especially when heating or cooling starts.
|
Intermittent Power Drop or Internal Overcurrent | View Details |
| – |
Thermostat screen is completely blank and does not power on at all.
|
No Power to Thermostat | View Details |
| – |
Thermostat shows humidity that is clearly incorrect (e.g., stuck at 10% or 90%) compared to other hygrometers.
|
Inaccurate Humidity Sensing | View Details |
| – |
Thermostat shows temperature that is clearly too high or too low compared to the actual room temperature.
|
Inaccurate Temperature Sensing | View Details |
| – |
Thermostat shows that the fan is off, but the indoor blower continues to run.
|
Fan Run‑On Not Controlled by Thermostat | View Details |
| – |
Thermostat will not connect to the mobile app or cannot be discovered during setup, even though Wi‑Fi is working.
|
App Pairing / Discovery Failure | View Details |
No matching codes found
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