Danfoss Ally
Danfoss Ally 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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CF
Display shows 'CF' or configuration error; thermostat does not follow expected heating mode or sensor selection.
Configuration Fault / Parameter Error
E1
Thermostat display shows E1 and heating does not start or stops shortly after calling for heat.
Temperature Sensor Failure
E2
Thermostat shows E2 and cannot correctly regulate room temperature; display may show dashes instead of temperature.
External Temperature Sensor Error
E3
E3 displayed and thermostat does not control the valve or relay; heating remains off or on continuously.
Actuator / Valve Drive Error
E4
E4 error on display; thermostat cannot complete valve calibration and may show fully open or fully closed symbol continuously.
Valve Calibration / Stroke Learning Failure
E5
E5 displayed and thermostat cannot communicate with the Danfoss Ally Gateway or app; remote control unavailable.
Zigbee Radio Communication Failure
E6
E6 error and thermostat does not switch the boiler or underfloor heating relay; no heat demand is sent.
Relay Output / Load Error
E7
E7 displayed; thermostat shows unstable or unrealistic room temperatures (e.g. -40°C or 99°C).
Temperature Measurement Out of Range
E8
E8 error and thermostat frequently restarts or becomes unresponsive when calling for heat.
Power Supply / Voltage Error
E9
E9 displayed; thermostat cannot complete firmware update or shows error during update via Ally app.
Firmware Update Failure
Er
Generic 'Er' or 'Err' message on display; thermostat does not follow commands or schedule.
General Internal Error
Hi
Display shows 'Hi' or maximum temperature; thermostat may stop heating control for safety.
Overtemperature Protection / High Temperature Alarm
Lo
Display shows 'Lo' or a low‑battery icon; thermostat becomes slow or unresponsive and may lose connection to gateway.
Low Battery Condition
No
Display shows 'No' or 'No Conn'; thermostat cannot be controlled from the Ally app and ignores remote schedules.
No Connection to Ally Gateway
Symptom
Boiler or heat source runs continuously even when all Danfoss Ally thermostats show no heat demand.
Boiler Stuck On / Ghost Demand
Symptom
Danfoss Ally radiator thermostat does not physically move the valve pin during setpoint changes; no motor sound is heard.
Motor Drive Failure
Symptom
Danfoss Ally radiator thermostat makes loud grinding or clicking noises during operation.
Noisy Valve Motor / Gear Train
Symptom
Radiator controlled by Danfoss Ally thermostat is always hot, even when the thermostat is set to a low temperature or off.
Valve Not Closing / Constant Heating
Symptom
Radiator controlled by Danfoss Ally thermostat stays cold even when the app and thermostat show a high setpoint and 'heating' demand.
No Heat from Radiator Despite Heat Demand
Symptom
Room never reaches the set temperature; it stays several degrees below the setpoint even though the thermostat calls for heat.
Underheating / Insufficient Heat Output
Symptom
Room temperature overshoots the setpoint by several degrees before the heating turns off.
Temperature Overshoot / Poor Regulation
Symptom
Thermostat buttons are unresponsive or require very hard presses to register.
Keypad / Button Failure
Symptom
Thermostat display is completely blank and does not respond to button presses or app commands.
No Power to Thermostat
Symptom
Thermostat display is very dim or unreadable unless viewed in the dark.
Display Backlight / LCD Visibility Issue
Symptom
Thermostat does not appear in the Ally app during initial setup, even when in pairing mode.
Pairing Failure with Ally Gateway
Symptom
Thermostat frequently loses connection in the Ally app and then reconnects later; schedules sometimes fail to run.
Intermittent Zigbee Connectivity
Symptom
Thermostat frequently switches the boiler on and off in short cycles, causing noise and wear.
Short Cycling / Rapid On-Off Control
Symptom
Thermostat or radiator valve area is warm to the touch and there is a faint smell of hot plastic.
Overheating Electronics / Localized Overtemperature
Symptom
Thermostat or radiator valve area shows signs of condensation or water droplets inside the housing.
Moisture Ingress / Condensation
Symptom
Thermostat shows a much higher or lower temperature than the actual room temperature by a consistent offset.
Temperature Calibration Offset
Symptom
Thermostat shows child lock or lock symbol and does not respond to button presses, but app control still works.
Child Lock / Keypad Lock Enabled
Symptom
Thermostat shows correct temperature but the boiler does not start when there is a heat demand.
No Boiler Firing on Heat Demand
Symptom
Thermostat shows different temperature or mode than what is displayed in the Ally app; changes take a long time to sync.
State Synchronization Delay
Symptom
Thermostat time and schedules reset after every power loss or battery change.
Loss of Configuration / Clock Reset
Symptom
Underfloor heating controlled by Danfoss Ally becomes excessively hot in some areas, risking floor damage.
Overheating Underfloor Heating
Symptom
Underfloor heating remains cold even though the Danfoss Ally thermostat calls for heat.
Underfloor Heating Not Heating
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| CF |
Display shows 'CF' or configuration error; thermostat does not follow expected heating mode or sensor selection.
|
Configuration Fault / Parameter Error | View Details |
| E1 |
Thermostat display shows E1 and heating does not start or stops shortly after calling for heat.
|
Temperature Sensor Failure | View Details |
| E2 |
Thermostat shows E2 and cannot correctly regulate room temperature; display may show dashes instead of temperature.
|
External Temperature Sensor Error | View Details |
| E3 |
E3 displayed and thermostat does not control the valve or relay; heating remains off or on continuously.
|
Actuator / Valve Drive Error | View Details |
| E4 |
E4 error on display; thermostat cannot complete valve calibration and may show fully open or fully closed symbol continuously.
|
Valve Calibration / Stroke Learning Failure | View Details |
| E5 |
E5 displayed and thermostat cannot communicate with the Danfoss Ally Gateway or app; remote control unavailable.
|
Zigbee Radio Communication Failure | View Details |
| E6 |
E6 error and thermostat does not switch the boiler or underfloor heating relay; no heat demand is sent.
|
Relay Output / Load Error | View Details |
| E7 |
E7 displayed; thermostat shows unstable or unrealistic room temperatures (e.g. -40°C or 99°C).
|
Temperature Measurement Out of Range | View Details |
| E8 |
E8 error and thermostat frequently restarts or becomes unresponsive when calling for heat.
|
Power Supply / Voltage Error | View Details |
| E9 |
E9 displayed; thermostat cannot complete firmware update or shows error during update via Ally app.
|
Firmware Update Failure | View Details |
| Er |
Generic 'Er' or 'Err' message on display; thermostat does not follow commands or schedule.
|
General Internal Error | View Details |
| Hi |
Display shows 'Hi' or maximum temperature; thermostat may stop heating control for safety.
|
Overtemperature Protection / High Temperature Alarm | View Details |
| Lo |
Display shows 'Lo' or a low‑battery icon; thermostat becomes slow or unresponsive and may lose connection to gateway.
|
Low Battery Condition | View Details |
| No |
Display shows 'No' or 'No Conn'; thermostat cannot be controlled from the Ally app and ignores remote schedules.
|
No Connection to Ally Gateway | View Details |
| – |
Boiler or heat source runs continuously even when all Danfoss Ally thermostats show no heat demand.
|
Boiler Stuck On / Ghost Demand | View Details |
| – |
Danfoss Ally radiator thermostat does not physically move the valve pin during setpoint changes; no motor sound is heard.
|
Motor Drive Failure | View Details |
| – |
Danfoss Ally radiator thermostat makes loud grinding or clicking noises during operation.
|
Noisy Valve Motor / Gear Train | View Details |
| – |
Radiator controlled by Danfoss Ally thermostat is always hot, even when the thermostat is set to a low temperature or off.
|
Valve Not Closing / Constant Heating | View Details |
| – |
Radiator controlled by Danfoss Ally thermostat stays cold even when the app and thermostat show a high setpoint and 'heating' demand.
|
No Heat from Radiator Despite Heat Demand | View Details |
| – |
Room never reaches the set temperature; it stays several degrees below the setpoint even though the thermostat calls for heat.
|
Underheating / Insufficient Heat Output | View Details |
| – |
Room temperature overshoots the setpoint by several degrees before the heating turns off.
|
Temperature Overshoot / Poor Regulation | View Details |
| – |
Thermostat buttons are unresponsive or require very hard presses to register.
|
Keypad / Button Failure | View Details |
| – |
Thermostat display is completely blank and does not respond to button presses or app commands.
|
No Power to Thermostat | View Details |
| – |
Thermostat display is very dim or unreadable unless viewed in the dark.
|
Display Backlight / LCD Visibility Issue | View Details |
| – |
Thermostat does not appear in the Ally app during initial setup, even when in pairing mode.
|
Pairing Failure with Ally Gateway | View Details |
| – |
Thermostat frequently loses connection in the Ally app and then reconnects later; schedules sometimes fail to run.
|
Intermittent Zigbee Connectivity | View Details |
| – |
Thermostat frequently switches the boiler on and off in short cycles, causing noise and wear.
|
Short Cycling / Rapid On-Off Control | View Details |
| – |
Thermostat or radiator valve area is warm to the touch and there is a faint smell of hot plastic.
|
Overheating Electronics / Localized Overtemperature | View Details |
| – |
Thermostat or radiator valve area shows signs of condensation or water droplets inside the housing.
|
Moisture Ingress / Condensation | View Details |
| – |
Thermostat shows a much higher or lower temperature than the actual room temperature by a consistent offset.
|
Temperature Calibration Offset | View Details |
| – |
Thermostat shows child lock or lock symbol and does not respond to button presses, but app control still works.
|
Child Lock / Keypad Lock Enabled | View Details |
| – |
Thermostat shows correct temperature but the boiler does not start when there is a heat demand.
|
No Boiler Firing on Heat Demand | View Details |
| – |
Thermostat shows different temperature or mode than what is displayed in the Ally app; changes take a long time to sync.
|
State Synchronization Delay | View Details |
| – |
Thermostat time and schedules reset after every power loss or battery change.
|
Loss of Configuration / Clock Reset | View Details |
| – |
Underfloor heating controlled by Danfoss Ally becomes excessively hot in some areas, risking floor damage.
|
Overheating Underfloor Heating | View Details |
| – |
Underfloor heating remains cold even though the Danfoss Ally thermostat calls for heat.
|
Underfloor Heating Not Heating | View Details |
No matching codes found
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