Heatline is a French boiler brand that is part of the Vaillant Group. Their Capriz and Capriz Plus combi boilers are popular in the UK social housing and residential market. Heatline fault codes use an F-prefix system that is closely related to Vaillant’s code structure, reflecting their shared technology platform.
Heatline Boiler Fault Codes
All Heatline Fault Codes 40
| Code | Fault | Severity | Type | View guide |
|---|---|---|---|---|
| F00 | Flow Temperature Sensor Fault The heating flow temperature sensor (F00) or return sensor (F01) has a wiring or sensor… | Medium | Engineer | View Guide |
| F01 | Flow NTC Fault Flow sensor has a fault. | Medium | Engineer | View Guide |
| F02 | Return NTC Fault Return sensor has a fault. | Medium | Engineer | View Guide |
| F03 | Overheat Safety thermostat activated. | High | Engineer | View Guide |
| F04 | Gas Valve Fault Gas valve not responding. | High | Engineer | View Guide |
| F05 | Fan Fault Fan not operating correctly. | High | Engineer | View Guide |
| F06 | Air Pressure Switch APS not detecting airflow. | High | Engineer | View Guide |
| F07 | PCB Fault Internal PCB error. | High | Engineer | View Guide |
| F08 | Low Water Pressure Pressure too low. | Low | DIY Check | View Guide |
| F09 | Pump Fault Pump not running. | High | Engineer | View Guide |
| F10 | DHW NTC Fault Hot water sensor faulty. | Medium | Engineer | View Guide |
| F11 | Condensate Blocked Condensate pipe blocked. | Medium | DIY Check | View Guide |
| F12 | Diverter Valve Fault Valve stuck. | Medium | Engineer | View Guide |
| F13 | Ignition Failure Failed to ignite. | High | Engineer | View Guide |
| F14 | Flame Lost Flame lost during operation. | High | Engineer | View Guide |
| F15 | Combustion Fault Air/gas mixture outside limits. | High | Engineer | View Guide |
| F16 | Pressure Sensor Fault Electronic sensor faulty. | Medium | Engineer | View Guide |
| F17 | Flame Detected After Shutdown Flame signal with gas off. | High | Engineer | View Guide |
| F18 | External Thermostat Fault Thermostat signal incorrect. | Medium | Engineer | View Guide |
| F19 | Rapid Temperature Rise Flow temp rising too fast. | High | Engineer | View Guide |
| F20 | Overheat Fault The boiler has overheated and the safety limiter has activated. Caused by poor circulation, low… | High | Engineer | View Guide |
| F21 | Flow/Return Reversed Sensors on wrong pipes. | Medium | Engineer | View Guide |
| F22 | Low Water Pressure System water pressure has dropped below the safe minimum for the boiler to operate. | Low | DIY Check | View Guide |
| F23 | Flow/Return Temperature Difference Too High The temperature difference between flow and return is excessive, indicating circulation problems. | Medium | Engineer | View Guide |
| F24 | Water Circulation Fault The boiler has detected insufficient water circulation. Isolation valves may be closed or the pump… | Medium | Engineer | View Guide |
| F25 | Outdoor Sensor Fault Outdoor sensor faulty. | Low | Engineer | View Guide |
| F26 | Gas Valve Motor Fault The gas valve motor has a fault, or the condensate pump is not operating correctly. | High | Engineer | View Guide |
| F27 | Flame Detection Fault The flame detection electrode has a fault. The boiler may ignite but cannot confirm the… | High | Engineer | View Guide |
| F28 | Ignition Failure The most common Heatline fault code. The boiler has failed to ignite. Very commonly caused… | Medium | DIY Check | View Guide |
| F29 | Flame Loss During Operation The boiler ignited but then lost its flame during operation. Often caused by gas supply… | Medium | DIY Check | View Guide |
| F30 | eBUS Fault Communication fault. | Medium | Engineer | View Guide |
| F31 | EEPROM Error PCB memory error. | High | Engineer | View Guide |
| F32 | Incorrect Air Pressure / Flue Fault The air pressure switch is not confirming correct airflow. May indicate a blocked flue, fan… | High | Engineer | View Guide |
| F33 | Mains Voltage Fault Voltage outside range. | Medium | Engineer | View Guide |
| F35 | Frost Protection Frost protection active. | Medium | DIY Check | View Guide |
| F49 | eBUS Communication Fault There is a communication fault on the eBUS — the communication bus between the boiler… | Medium | Engineer | View Guide |
| F72 | Flow/Return Sensor Temperature Drift A permanent temperature difference has been detected between the flow and return sensors, indicating a… | Medium | Engineer | View Guide |
| F73 | Heating Circuit Pressure Sensor Fault The heating circuit water pressure sensor has a fault. | Medium | Engineer | View Guide |
| F76 | Thermal Fuse Fault The thermal fuse on the heat exchanger has blown due to extreme overheating. The heat… | High | Engineer | View Guide |
| F83 | No Water Detected / Dry Fire The boiler has fired but no temperature rise was detected, indicating the system has no… | High | Engineer | View Guide |