Vaillant 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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F.01
Vaillant smart thermostat display shows F.01 and cannot communicate with the boiler; heating does not start.
eBUS Communication Failure
F.02
Smart thermostat shows F.02 and cannot detect the boiler; no heating control via app or room unit.
Boiler Not Detected on eBUS
F.03
Vaillant smart thermostat shows F.03 and cannot connect to the Vaillant internet module; app control unavailable.
Local Gateway / Internet Module Communication Error
F.04
Smart thermostat displays F.04 and cannot detect any wireless receiver or boiler interface; heating does not respond.
Wireless Receiver / Boiler Interface Not Found
F.05
Vaillant smart thermostat shows F.05 and the room temperature reading is clearly wrong (e.g. 5°C or 50°C indoors).
Internal Room Temperature Sensor Fault
F.06
Smart thermostat shows F.06 and cannot read the external outdoor sensor; weather compensation not working.
Outdoor Temperature Sensor Fault
F.07
Vaillant smart thermostat shows F.07 and cannot control the heating zone valve; selected zone does not heat.
Heating Zone Actuator / Relay Output Fault
F.08
Smart thermostat shows F.08 and hot water cylinder temperature is not displayed; hot water control limited.
Cylinder Temperature Sensor Fault
F.09
Vaillant smart thermostat shows F.09 and schedules cannot be saved or recalled correctly.
Internal Memory / Configuration Error
F.10
Smart thermostat shows F.10 and cannot connect to the internet; remote control via Vaillant app not available.
Wi‑Fi / Network Connection Failure
F.11
Vaillant smart thermostat shows F.11 and the time/date keep resetting or drifting significantly.
Real‑Time Clock / Time Synchronisation Error
F.12
Smart thermostat shows F.12 and refuses to control heating because the system configuration is incomplete.
System Configuration / Commissioning Error
F.13
Vaillant smart thermostat shows F.13 and one or more wireless room units frequently drop offline.
Intermittent Wireless Link Failure
F.14
Smart thermostat shows F.14 and refuses to start heating because of a detected wiring fault.
Incorrect Wiring / Short Circuit Detection
F.15
Vaillant smart thermostat shows F.15 and the display is very dim or unreadable, sometimes flickering.
Display / Backlight Power Fault
F.16
Smart thermostat shows F.16 and the boiler does not respond to temperature changes or schedules.
Control Signal Output Fault
F.17
Vaillant smart thermostat shows F.17 and reports that maximum number of devices or zones has been exceeded.
Device Limit / Address Conflict
F.18
Smart thermostat shows F.18 and the Vaillant app cannot access system data even though the device is online.
Cloud Service / Account Linking Error
F.19
Vaillant smart thermostat shows F.19 and reports low battery or power supply issues.
Low Power / Battery Fault
F.20
Smart thermostat shows F.20 and indicates an internal temperature overheat or hardware protection event.
Internal Overtemperature Protection
Symptom
Condensation or visible moisture is present inside the Vaillant smart thermostat housing.
Moisture Ingress / Condensation Damage Risk
Symptom
Heating remains on even when the Vaillant smart thermostat is set to OFF or a low temperature.
Heating Stuck On / Runaway Heating
Symptom
Hot water does not heat according to the Vaillant smart thermostat’s hot water schedule.
Domestic Hot Water Control Fault
Symptom
Room temperature does not reach setpoint even though the Vaillant smart thermostat shows heating as 'ON'.
Underheating / Insufficient Heat Output
Symptom
Room temperature shown on the Vaillant smart thermostat differs significantly from other thermometers in the same room.
Temperature Calibration / Location Error
Symptom
Smart thermostat display is completely blank or frozen and does not respond to touch or buttons.
Thermostat Power Loss / Lockup
Symptom
Smart thermostat frequently reboots or restarts by itself, interrupting heating control.
Unstable Power / Firmware Crash
Symptom
Smart thermostat or Vaillant internet module feels unusually hot to the touch during normal operation.
Overheating of Control Electronics
Symptom
Vaillant smart thermostat buttons or touchscreen are unresponsive or register incorrect presses.
User Interface / Keypad Fault
Symptom
Vaillant smart thermostat cannot be added to the Vaillant app; pairing or registration fails repeatedly.
Onboarding / Pairing Failure
Symptom
Vaillant smart thermostat frequently loses connection to the Vaillant app, showing offline status intermittently.
Intermittent Cloud Connectivity
Symptom
Vaillant smart thermostat or gateway emits a buzzing or clicking noise during operation.
Electrical Noise / Relay Chatter
Symptom
Vaillant smart thermostat schedules do not follow the programmed times; heating turns on or off at unexpected times.
Scheduling / Time Control Fault
Symptom
Vaillant smart thermostat shows 'No boiler connected' or similar message, but the boiler is installed and powered.
Boiler Detection / Identification Failure
Symptom
Vaillant smart thermostat shows 'Service due' or similar maintenance reminder and user is unsure how to clear it.
Service Interval Reminder
Symptom
Vaillant smart thermostat shows large temperature swings, with the room alternately too hot and too cold.
Poor Temperature Control / Overshoot
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| F.01 |
Vaillant smart thermostat display shows F.01 and cannot communicate with the boiler; heating does not start.
|
eBUS Communication Failure | View Details |
| F.02 |
Smart thermostat shows F.02 and cannot detect the boiler; no heating control via app or room unit.
|
Boiler Not Detected on eBUS | View Details |
| F.03 |
Vaillant smart thermostat shows F.03 and cannot connect to the Vaillant internet module; app control unavailable.
|
Local Gateway / Internet Module Communication Error | View Details |
| F.04 |
Smart thermostat displays F.04 and cannot detect any wireless receiver or boiler interface; heating does not respond.
|
Wireless Receiver / Boiler Interface Not Found | View Details |
| F.05 |
Vaillant smart thermostat shows F.05 and the room temperature reading is clearly wrong (e.g. 5°C or 50°C indoors).
|
Internal Room Temperature Sensor Fault | View Details |
| F.06 |
Smart thermostat shows F.06 and cannot read the external outdoor sensor; weather compensation not working.
|
Outdoor Temperature Sensor Fault | View Details |
| F.07 |
Vaillant smart thermostat shows F.07 and cannot control the heating zone valve; selected zone does not heat.
|
Heating Zone Actuator / Relay Output Fault | View Details |
| F.08 |
Smart thermostat shows F.08 and hot water cylinder temperature is not displayed; hot water control limited.
|
Cylinder Temperature Sensor Fault | View Details |
| F.09 |
Vaillant smart thermostat shows F.09 and schedules cannot be saved or recalled correctly.
|
Internal Memory / Configuration Error | View Details |
| F.10 |
Smart thermostat shows F.10 and cannot connect to the internet; remote control via Vaillant app not available.
|
Wi‑Fi / Network Connection Failure | View Details |
| F.11 |
Vaillant smart thermostat shows F.11 and the time/date keep resetting or drifting significantly.
|
Real‑Time Clock / Time Synchronisation Error | View Details |
| F.12 |
Smart thermostat shows F.12 and refuses to control heating because the system configuration is incomplete.
|
System Configuration / Commissioning Error | View Details |
| F.13 |
Vaillant smart thermostat shows F.13 and one or more wireless room units frequently drop offline.
|
Intermittent Wireless Link Failure | View Details |
| F.14 |
Smart thermostat shows F.14 and refuses to start heating because of a detected wiring fault.
|
Incorrect Wiring / Short Circuit Detection | View Details |
| F.15 |
Vaillant smart thermostat shows F.15 and the display is very dim or unreadable, sometimes flickering.
|
Display / Backlight Power Fault | View Details |
| F.16 |
Smart thermostat shows F.16 and the boiler does not respond to temperature changes or schedules.
|
Control Signal Output Fault | View Details |
| F.17 |
Vaillant smart thermostat shows F.17 and reports that maximum number of devices or zones has been exceeded.
|
Device Limit / Address Conflict | View Details |
| F.18 |
Smart thermostat shows F.18 and the Vaillant app cannot access system data even though the device is online.
|
Cloud Service / Account Linking Error | View Details |
| F.19 |
Vaillant smart thermostat shows F.19 and reports low battery or power supply issues.
|
Low Power / Battery Fault | View Details |
| F.20 |
Smart thermostat shows F.20 and indicates an internal temperature overheat or hardware protection event.
|
Internal Overtemperature Protection | View Details |
| – |
Condensation or visible moisture is present inside the Vaillant smart thermostat housing.
|
Moisture Ingress / Condensation Damage Risk | View Details |
| – |
Heating remains on even when the Vaillant smart thermostat is set to OFF or a low temperature.
|
Heating Stuck On / Runaway Heating | View Details |
| – |
Hot water does not heat according to the Vaillant smart thermostat’s hot water schedule.
|
Domestic Hot Water Control Fault | View Details |
| – |
Room temperature does not reach setpoint even though the Vaillant smart thermostat shows heating as 'ON'.
|
Underheating / Insufficient Heat Output | View Details |
| – |
Room temperature shown on the Vaillant smart thermostat differs significantly from other thermometers in the same room.
|
Temperature Calibration / Location Error | View Details |
| – |
Smart thermostat display is completely blank or frozen and does not respond to touch or buttons.
|
Thermostat Power Loss / Lockup | View Details |
| – |
Smart thermostat frequently reboots or restarts by itself, interrupting heating control.
|
Unstable Power / Firmware Crash | View Details |
| – |
Smart thermostat or Vaillant internet module feels unusually hot to the touch during normal operation.
|
Overheating of Control Electronics | View Details |
| – |
Vaillant smart thermostat buttons or touchscreen are unresponsive or register incorrect presses.
|
User Interface / Keypad Fault | View Details |
| – |
Vaillant smart thermostat cannot be added to the Vaillant app; pairing or registration fails repeatedly.
|
Onboarding / Pairing Failure | View Details |
| – |
Vaillant smart thermostat frequently loses connection to the Vaillant app, showing offline status intermittently.
|
Intermittent Cloud Connectivity | View Details |
| – |
Vaillant smart thermostat or gateway emits a buzzing or clicking noise during operation.
|
Electrical Noise / Relay Chatter | View Details |
| – |
Vaillant smart thermostat schedules do not follow the programmed times; heating turns on or off at unexpected times.
|
Scheduling / Time Control Fault | View Details |
| – |
Vaillant smart thermostat shows 'No boiler connected' or similar message, but the boiler is installed and powered.
|
Boiler Detection / Identification Failure | View Details |
| – |
Vaillant smart thermostat shows 'Service due' or similar maintenance reminder and user is unsure how to clear it.
|
Service Interval Reminder | View Details |
| – |
Vaillant smart thermostat shows large temperature swings, with the room alternately too hot and too cold.
|
Poor Temperature Control / Overshoot | View Details |
No matching codes found
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