Bosch EasyControl
Bosch EasyControl 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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C1
Bosch EasyControl display shows error C1 and heating does not start or stops shortly after demand.
OpenTherm Communication Failure
C10
Bosch EasyControl shows error C10 and fails to complete pairing with the Bosch EasyControl app or Bosch ID account.
Account Linking or Cloud Registration Error
C11
Bosch EasyControl displays error C11 and schedules or settings frequently reset or are lost after power interruptions.
Non-Volatile Memory or Backup Power Fault
C12
Bosch EasyControl shows error C12 and cannot control a second heating circuit or zone as configured.
Multi-Zone or Second Circuit Control Fault
C13
Bosch EasyControl displays error C13 and reports that geofencing or presence detection is unavailable.
Presence Detection / Geofencing Service Fault
C14
Bosch EasyControl shows error C14 and energy usage or consumption data is missing or clearly incorrect.
Energy Monitoring / Data Acquisition Fault
C15
Bosch EasyControl displays error C15 and fails to control underfloor heating circuits correctly (overheating or underheating).
Underfloor Heating Control Configuration Fault
C16
Bosch EasyControl shows error C16 and indicates that the boiler safety lockout has been triggered via the control interface.
Boiler Lockout Reported to EasyControl
C17
Bosch EasyControl displays error C17 and indicates that the external temperature sensor (for weather compensation) is not detected or faulty.
Outdoor Temperature Sensor Fault
C18
Bosch EasyControl shows error C18 and reports that the internal humidity or air quality sensor (if present) is malfunctioning.
Internal Humidity / Air Quality Sensor Fault
C19
Bosch EasyControl displays error C19 and cannot complete time synchronization or shows incorrect time repeatedly.
Time Synchronization / NTP Error
C2
Bosch EasyControl shows error C2 and cannot control the boiler; heating remains off or runs only in basic on/off mode.
Boiler Not Detected or Unsupported Protocol
C20
Bosch EasyControl shows error C20 and indicates that the boiler modulation control is limited or disabled.
Modulation Control Limitation / Degraded Mode
C3
Bosch EasyControl displays error C3 and the thermostat cannot complete initial setup or loses configuration.
Internal Configuration or Firmware Error
C4
Bosch EasyControl shows error C4 and cannot detect or control the heating circuit correctly.
Heating Circuit Configuration or Sensor Error
C5
Bosch EasyControl displays error C5 and fails to control domestic hot water (DHW) or cylinder temperature.
DHW / Cylinder Sensor or Control Fault
C6
Bosch EasyControl shows error C6 and the thermostat cannot connect to the internet or Bosch cloud services.
Wi‑Fi or Cloud Connectivity Failure
C7
Bosch EasyControl displays error C7 and cannot detect paired Bosch Smart Radiator Thermostats or wireless room sensors.
Wireless Accessory Communication Failure
C8
Bosch EasyControl shows error C8 and the display or touch interface is unresponsive or partially functional.
Touchscreen or Display Interface Fault
C9
Bosch EasyControl displays error C9 and room temperature readings are clearly incorrect (e.g., showing 5–10°C off actual).
Internal Room Temperature Sensor Fault
Symptom
Bosch EasyControl app cannot find or connect to the thermostat on the local network, even though the thermostat shows as connected to Wi‑Fi.
Local Network Discovery / App Connectivity Issue
Symptom
Bosch EasyControl appears to work, but room temperature overshoots the setpoint by several degrees before the boiler turns off.
Poor Temperature Control / Overshoot
Symptom
Bosch EasyControl backlight or display is very dim or flickers, making it hard to read.
Display Backlight Degradation or Power Issue
Symptom
Bosch EasyControl becomes very warm to the touch and may behave erratically.
Thermostat Overheating
Symptom
Bosch EasyControl calls for heat but radiators remain cold while hot water still works on a combi boiler.
Heating Circuit Isolation or Valve Fault (Control Side)
Symptom
Bosch EasyControl causes the boiler to cycle on and off frequently (short cycling), even with small temperature changes.
Short Cycling of Boiler Due to Control Settings
Symptom
Bosch EasyControl display is completely blank and unresponsive; heating does not respond to thermostat.
No Power to EasyControl
Symptom
Bosch EasyControl does not detect or control Bosch Smart Radiator Thermostats in certain rooms, leading to uneven heating.
Partial Wireless Zone Communication Failure
Symptom
Bosch EasyControl does not turn on heating for certain rooms controlled by Bosch Smart Radiator Thermostats, even when those rooms are cold.
Zone Demand Not Propagating to Boiler
Symptom
Bosch EasyControl emits unusual buzzing or high-pitched noise during operation.
Electrical Noise from Internal Components
Symptom
Bosch EasyControl frequently loses Wi‑Fi connection, causing the app to show the thermostat as offline.
Intermittent Wi‑Fi Connectivity
Symptom
Bosch EasyControl powers on but frequently reboots or restarts by itself, sometimes losing connection to the boiler or Wi‑Fi.
Intermittent Power or Internal Overheat Fault
Symptom
Bosch EasyControl schedules do not run as expected; heating turns on or off at wrong times.
Scheduling / Time Configuration Error
Symptom
Bosch EasyControl screen is on but touch input does not respond or responds only intermittently.
Unresponsive Touchscreen
Symptom
Bosch EasyControl shows domestic hot water as off or unavailable, but the boiler is capable of DHW control.
DHW Control Disabled or Misconfigured
Symptom
Bosch EasyControl shows much higher room temperature than actual, so heating rarely comes on.
Over-Reading Room Temperature
Symptom
Bosch EasyControl shows much lower room temperature than actual, causing the boiler to run almost constantly.
Under-Reading Room Temperature
Symptom
Bosch EasyControl shows normal operation but the boiler does not fire for heating when there is a demand.
No Heat Demand Reaching Boiler
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| C1 |
Bosch EasyControl display shows error C1 and heating does not start or stops shortly after demand.
|
OpenTherm Communication Failure | View Details |
| C10 |
Bosch EasyControl shows error C10 and fails to complete pairing with the Bosch EasyControl app or Bosch ID account.
|
Account Linking or Cloud Registration Error | View Details |
| C11 |
Bosch EasyControl displays error C11 and schedules or settings frequently reset or are lost after power interruptions.
|
Non-Volatile Memory or Backup Power Fault | View Details |
| C12 |
Bosch EasyControl shows error C12 and cannot control a second heating circuit or zone as configured.
|
Multi-Zone or Second Circuit Control Fault | View Details |
| C13 |
Bosch EasyControl displays error C13 and reports that geofencing or presence detection is unavailable.
|
Presence Detection / Geofencing Service Fault | View Details |
| C14 |
Bosch EasyControl shows error C14 and energy usage or consumption data is missing or clearly incorrect.
|
Energy Monitoring / Data Acquisition Fault | View Details |
| C15 |
Bosch EasyControl displays error C15 and fails to control underfloor heating circuits correctly (overheating or underheating).
|
Underfloor Heating Control Configuration Fault | View Details |
| C16 |
Bosch EasyControl shows error C16 and indicates that the boiler safety lockout has been triggered via the control interface.
|
Boiler Lockout Reported to EasyControl | View Details |
| C17 |
Bosch EasyControl displays error C17 and indicates that the external temperature sensor (for weather compensation) is not detected or faulty.
|
Outdoor Temperature Sensor Fault | View Details |
| C18 |
Bosch EasyControl shows error C18 and reports that the internal humidity or air quality sensor (if present) is malfunctioning.
|
Internal Humidity / Air Quality Sensor Fault | View Details |
| C19 |
Bosch EasyControl displays error C19 and cannot complete time synchronization or shows incorrect time repeatedly.
|
Time Synchronization / NTP Error | View Details |
| C2 |
Bosch EasyControl shows error C2 and cannot control the boiler; heating remains off or runs only in basic on/off mode.
|
Boiler Not Detected or Unsupported Protocol | View Details |
| C20 |
Bosch EasyControl shows error C20 and indicates that the boiler modulation control is limited or disabled.
|
Modulation Control Limitation / Degraded Mode | View Details |
| C3 |
Bosch EasyControl displays error C3 and the thermostat cannot complete initial setup or loses configuration.
|
Internal Configuration or Firmware Error | View Details |
| C4 |
Bosch EasyControl shows error C4 and cannot detect or control the heating circuit correctly.
|
Heating Circuit Configuration or Sensor Error | View Details |
| C5 |
Bosch EasyControl displays error C5 and fails to control domestic hot water (DHW) or cylinder temperature.
|
DHW / Cylinder Sensor or Control Fault | View Details |
| C6 |
Bosch EasyControl shows error C6 and the thermostat cannot connect to the internet or Bosch cloud services.
|
Wi‑Fi or Cloud Connectivity Failure | View Details |
| C7 |
Bosch EasyControl displays error C7 and cannot detect paired Bosch Smart Radiator Thermostats or wireless room sensors.
|
Wireless Accessory Communication Failure | View Details |
| C8 |
Bosch EasyControl shows error C8 and the display or touch interface is unresponsive or partially functional.
|
Touchscreen or Display Interface Fault | View Details |
| C9 |
Bosch EasyControl displays error C9 and room temperature readings are clearly incorrect (e.g., showing 5–10°C off actual).
|
Internal Room Temperature Sensor Fault | View Details |
| – |
Bosch EasyControl app cannot find or connect to the thermostat on the local network, even though the thermostat shows as connected to Wi‑Fi.
|
Local Network Discovery / App Connectivity Issue | View Details |
| – |
Bosch EasyControl appears to work, but room temperature overshoots the setpoint by several degrees before the boiler turns off.
|
Poor Temperature Control / Overshoot | View Details |
| – |
Bosch EasyControl backlight or display is very dim or flickers, making it hard to read.
|
Display Backlight Degradation or Power Issue | View Details |
| – |
Bosch EasyControl becomes very warm to the touch and may behave erratically.
|
Thermostat Overheating | View Details |
| – |
Bosch EasyControl calls for heat but radiators remain cold while hot water still works on a combi boiler.
|
Heating Circuit Isolation or Valve Fault (Control Side) | View Details |
| – |
Bosch EasyControl causes the boiler to cycle on and off frequently (short cycling), even with small temperature changes.
|
Short Cycling of Boiler Due to Control Settings | View Details |
| – |
Bosch EasyControl display is completely blank and unresponsive; heating does not respond to thermostat.
|
No Power to EasyControl | View Details |
| – |
Bosch EasyControl does not detect or control Bosch Smart Radiator Thermostats in certain rooms, leading to uneven heating.
|
Partial Wireless Zone Communication Failure | View Details |
| – |
Bosch EasyControl does not turn on heating for certain rooms controlled by Bosch Smart Radiator Thermostats, even when those rooms are cold.
|
Zone Demand Not Propagating to Boiler | View Details |
| – |
Bosch EasyControl emits unusual buzzing or high-pitched noise during operation.
|
Electrical Noise from Internal Components | View Details |
| – |
Bosch EasyControl frequently loses Wi‑Fi connection, causing the app to show the thermostat as offline.
|
Intermittent Wi‑Fi Connectivity | View Details |
| – |
Bosch EasyControl powers on but frequently reboots or restarts by itself, sometimes losing connection to the boiler or Wi‑Fi.
|
Intermittent Power or Internal Overheat Fault | View Details |
| – |
Bosch EasyControl schedules do not run as expected; heating turns on or off at wrong times.
|
Scheduling / Time Configuration Error | View Details |
| – |
Bosch EasyControl screen is on but touch input does not respond or responds only intermittently.
|
Unresponsive Touchscreen | View Details |
| – |
Bosch EasyControl shows domestic hot water as off or unavailable, but the boiler is capable of DHW control.
|
DHW Control Disabled or Misconfigured | View Details |
| – |
Bosch EasyControl shows much higher room temperature than actual, so heating rarely comes on.
|
Over-Reading Room Temperature | View Details |
| – |
Bosch EasyControl shows much lower room temperature than actual, causing the boiler to run almost constantly.
|
Under-Reading Room Temperature | View Details |
| – |
Bosch EasyControl shows normal operation but the boiler does not fire for heating when there is a demand.
|
No Heat Demand Reaching Boiler | View Details |
No matching codes found
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