Ideal Heating has been manufacturing boilers in Hull since 1906 and is one of the UK’s largest domestic boiler brands. Their Logic, Logic+, and Vogue ranges are extremely popular. Ideal fault codes use ‘F’ prefix codes for faults that may self-reset, while ‘L’ prefix codes are lockout faults that require a manual reset.
Ideal Boiler Fault Codes
All Ideal Fault Codes 77
| Code | Fault | Severity | Type | View guide |
|---|---|---|---|---|
| C0 | Fan Fault — Fan Not Running The fan has failed to start or is not reaching operating speed. C0 is a… | High | Engineer | View Guide |
| C0 0 | Fan Not Running at Start (Sub-code) The fan is not running at the point in the start sequence where it is… | High | Engineer | View Guide |
| C1 | Flue Temperature Too High The flue gas temperature has exceeded the safe limit. The boiler has shut down to… | High | Engineer | View Guide |
| C2 | Fan Fault — Speed Out of Range The fan speed is outside the expected operating range — either too slow or too… | High | Engineer | View Guide |
| C3 | Air Pressure Switch Open The air pressure switch is not closing when the fan runs. The boiler cannot confirm… | High | Engineer | View Guide |
| C4 | Diverter Valve Fault The diverter valve is stuck or not switching. | Medium | Engineer | View Guide |
| C5 | Rapid Temperature Rise Flow temperature rising too quickly, indicating poor circulation. | High | Engineer | View Guide |
| C6 | Flow/Return Differential Too Large The temperature gap between flow and return is abnormal. | Medium | Engineer | View Guide |
| C7 | Outdoor Sensor Fault The outdoor temperature sensor is faulty. | Low | Engineer | View Guide |
| C8 | eBUS Communication Fault The eBUS line has a fault. | Medium | Engineer | View Guide |
| C9 | EEPROM Error PCB memory error. | High | Engineer | View Guide |
| F0 | Frost Protection Active Frost protection cycles are running. | Medium | DIY Check | View Guide |
| F1 | Low Water Pressure The boiler's water pressure has dropped below the minimum operating level. One of the most… | Low | DIY Check | View Guide |
| F10 | DHW Temperature Sensor Fault The domestic hot water temperature sensor has a fault. On combi boilers, this prevents safe… | Medium | Engineer | View Guide |
| F11 | Cylinder Sensor Fault The hot water cylinder temperature sensor has a fault. Relevant on system boilers paired with… | Medium | Engineer | View Guide |
| F12 | Flame Loss During Operation The boiler had a stable flame but lost it during operation. This can be caused… | High | Engineer | View Guide |
| F13 | Gas Pressure Sensor Fault The gas pressure sensor is giving an out-of-range reading, preventing safe operation. | High | Engineer | View Guide |
| F14 | Gas Valve Fault The gas valve is not responding correctly to commands from the PCB. | High | Engineer | View Guide |
| F15 | PCB Communication Fault The printed circuit board (PCB) has an internal communication error. Key boiler components cannot communicate… | High | Engineer | View Guide |
| F16 | Fan Fault The fan is not running at the correct speed or has stopped. The boiler cannot… | High | Engineer | View Guide |
| F17 | Pump Over-Run Fault The pump did not stop after the burner shut down. | Medium | Engineer | View Guide |
| F18 | Condensate Blocked The condensate drain is blocked or frozen. | Medium | DIY Check | View Guide |
| F19 | Flue Gas Overheat The flue gas temperature is too high. | High | Engineer | View Guide |
| F2 | Flame Loss The boiler has lost its flame during operation or failed to ignite. | Medium | DIY Check | View Guide |
| F20 | Pressure Sensor Fault The electronic water pressure sensor is giving incorrect readings. | Medium | Engineer | View Guide |
| F21 | Pump Fault The circulation pump is not running or is blocked. | High | Engineer | View Guide |
| F22 | Gas Valve Fault The gas valve is not responding correctly. | High | Engineer | View Guide |
| F23 | Flame Detected After Shutdown Flame signal with gas valve closed. | High | Engineer | View Guide |
| F24 | Outdoor Sensor Fault Outdoor sensor faulty or disconnected. | Low | Engineer | View Guide |
| F25 | eBUS Fault Communication line fault. | Medium | Engineer | View Guide |
| F26 | Phase/Neutral Reversed Electrical polarity reversed. | High | Engineer | View Guide |
| F27 | EEPROM Error PCB memory error. | High | Engineer | View Guide |
| F28 | Coding Plug Fault Coding plug unreadable. | High | Engineer | View Guide |
| F29 | Mains Voltage Fault Voltage outside range. | Medium | Engineer | View Guide |
| F3 | Fan Fault The boiler fan is not operating at the required speed, preventing safe ignition. | High | Engineer | View Guide |
| F30 | Combustion Fault Air/gas outside limits. | High | Engineer | View Guide |
| F4 | Flow Thermistor Fault The flow temperature sensor (thermistor) is giving an incorrect reading or has failed. | Medium | Engineer | View Guide |
| F5 | Return Thermistor Fault The return temperature sensor is giving an incorrect reading or has failed. | Medium | Engineer | View Guide |
| F6 | Outside Sensor Fault The external temperature sensor (used for weather compensation) is faulty or not connected. This does… | Low | Engineer | View Guide |
| F7 | Low Mains Voltage The mains voltage supply to the boiler has dropped below the safe minimum (185V). | Medium | Engineer | View Guide |
| F8 | Flow Thermistor - Out of Range High The flow temperature sensor is reading higher than its maximum expected value, indicating a sensor… | High | Engineer | View Guide |
| F9 | Unconfigured PCB The Printed Circuit Board has not been configured correctly. This almost always occurs after a… | Medium | Engineer | View Guide |
| FA | Flow/Return Sensors Reversed (Regular Boilers) On Ideal Logic Max and Logic Plus regular (heat-only) boilers, code FA indicates the flow… | Medium | Engineer | View Guide |
| FD | Condensate Blocked / Frozen The condensate drain system is blocked or frozen. FD is Ideal's code for a blocked… | Medium | DIY Check | View Guide |
| FN | Flame Loss (Alternative Code) On some Ideal models, FN is displayed alongside or instead of F2 to indicate flame… | Medium | DIY Check | View Guide |
| FU | Temperature Difference Too High — Check Isolation Valves The temperature difference between the flow and return is greater than 50°C. The boiler is… | Medium | DIY Check | View Guide |
| GV | Gas Valve Fault The gas valve is not responding to commands from the PCB. | High | Engineer | View Guide |
| HL | Overheat Lockout The boiler exceeded maximum safe temperature. | High | Engineer | View Guide |
| HT | DHW Overheat The domestic hot water temperature has exceeded safe limits. | High | Engineer | View Guide |
| L0 | Safety Limit Lockout (Generic) A safety device has operated. This is a catch-all lockout code when a specific fault… | High | Engineer | View Guide |
| L1 | Flow Overheat / No Water Flow Lockout The boiler has locked out because the flow temperature is too high or no water… | High | Engineer | View Guide |
| L10 | Overheat Lockout — Maximum Temperature Exceeded The boiler has reached its absolute maximum temperature and locked out. A more severe overheat… | High | Engineer | View Guide |
| L11 | Central Heating Thermistor Fault The central heating NTC thermistor is reading outside its normal range. The sensor may have… | Medium | Engineer | View Guide |
| L12 | Return NTC Fault Return NTC sensor faulty. | Medium | Engineer | View Guide |
| L13 | DHW NTC Fault Hot water sensor faulty. | Medium | Engineer | View Guide |
| L14 | Flow NTC Short Circuit Flow NTC wiring shorted. | Medium | Engineer | View Guide |
| L15 | Return NTC Short Circuit Return NTC wiring shorted. | Medium | Engineer | View Guide |
| L16 | DHW NTC Short Circuit DHW NTC wiring shorted. | Medium | Engineer | View Guide |
| L17 | APS Open Air pressure switch not confirming airflow. | High | Engineer | View Guide |
| L18 | Rapid Temperature Rise Flow temp rising too fast. | High | Engineer | View Guide |
| L19 | Flow/Return Differential Fault Temperature gap abnormal. | Medium | Engineer | View Guide |
| L2 | Ignition Lockout The boiler has locked out after failing to ignite or losing its flame. A persistent… | Medium | DIY Check | View Guide |
| L20 | Condensate Blocked Condensate drain blocked. | Medium | DIY Check | View Guide |
| L3 | Fan Lockout The boiler fan has failed to reach the required speed after multiple attempts. | High | Engineer | View Guide |
| L4 | Overheat Lockout The boiler's safety overheat thermostat has triggered a lockout due to excessively high temperatures. | High | Engineer | View Guide |
| L5 | Too Many Resets The boiler has been reset 5 times within 15 minutes and has entered a protective… | Medium | DIY Check | View Guide |
| L6 | False Flame Lockout The boiler has detected an ionisation signal when the gas valve should be closed. This… | High | Engineer | View Guide |
| L7 | DHW Thermistor Lockout The domestic hot water temperature sensor has caused a lockout — either due to a… | High | Engineer | View Guide |
| L8 | Flue Temperature Lockout The flue gas temperature sensor has detected an unsafe temperature, causing a lockout. | High | Engineer | View Guide |
| L9 | PCB Fault / Unconfigured The PCB has an internal fault or has not been configured correctly. L9 is the… | High | Engineer | View Guide |
| LC | Too Many Resets (5 Within 15 Minutes) The boiler has been reset 5 or more times within 15 minutes and has entered… | Medium | DIY Check | View Guide |
| LE | Low Water Pressure System pressure is below minimum. | Low | DIY Check | View Guide |
| LF | Low Gas Pressure Warning The boiler has detected that the gas supply pressure is lower than expected, which may… | Medium | Engineer | View Guide |
| LN | Flame Loss Lockout (Alternative Code) On some Ideal models, LN is a lockout version of FN/F2, indicating repeated flame loss… | Medium | DIY Check | View Guide |
| LP | Low Pressure Lockout System pressure critically low — boiler locked out. | Medium | DIY Check | View Guide |
| PF | PCB Fault The printed circuit board has an internal error. | High | Engineer | View Guide |
| SE | Sensor Error One or more NTC temperature sensors are reading outside expected range. | Medium | Engineer | View Guide |