Baxi is a British boiler brand founded in Bolton in 1866, making it one of the oldest heating manufacturers in the UK. Today they are part of the BDR Thermea Group and produce a wide range of combi, system, and heat-only boilers.
Baxi Boiler Fault Codes
All Baxi Fault Codes 84
| Code | Fault | Severity | Type | View guide |
|---|---|---|---|---|
| 111 | Maximum Flow Temperature Limit Reached (EcoBlue) On Baxi EcoBlue boilers, code 111 indicates the maximum flow temperature limit has been reached… | Medium | Engineer | View Guide |
| 117 | Water Pressure Too High System water pressure has exceeded the safe maximum — likely above 2.9 bar. Do NOT… | Medium | Engineer | View Guide |
| 118 | Water Pressure Too Low (EcoBlue) On Baxi EcoBlue boilers, code 118 indicates system water pressure is too low (below 0.5… | Low | DIY Check | View Guide |
| 127 | Legionella Protection Temperature Not Reached The boiler attempted a legionella prevention cycle (periodic high-temperature DHW heating) but could not reach… | Low | Engineer | View Guide |
| 162 | Air Pressure Switch Fault (EcoBlue) On Baxi EcoBlue boilers, code 162 indicates the air pressure switch has a fault —… | High | Engineer | View Guide |
| 166 | Air Pressure Switch Fault (Secondary) A secondary air pressure switch fault on Baxi EcoBlue boilers. | High | Engineer | View Guide |
| 2 RED FLASHES | Boiler Overheat Tripped (EcoBlue/MainEco) On Baxi EcoBlue and MainEco boilers, 2 red flashes indicates the overheat thermostat has tripped. | High | Engineer | View Guide |
| 270 | Dry Fire / No Water Circulation The boiler has detected firing without adequate water circulation — a 'dry fire' condition. The… | High | Engineer | View Guide |
| 3 GREEN FLASHES | Temporary Flame Loss (EcoBlue/MainEco) On Baxi EcoBlue and MainEco boilers, 3 green flashes indicates a temporary flame loss. The… | Low | DIY Check | View Guide |
| 3 RED FLASHES | Ignition Failure — 5 Attempts (EcoBlue/MainEco) On Baxi EcoBlue and MainEco boilers, 3 red flashes means the boiler has failed to… | Medium | DIY Check | View Guide |
| 4 RED FLASHES | Fan Fault (EcoBlue/MainEco) On Baxi EcoBlue and MainEco boilers, 4 red flashes indicates a fan fault. | High | Engineer | View Guide |
| 432 | Earth Connector Error (EcoBlue) The boiler has detected an issue with the earth connection in the electrical supply. | High | Engineer | View Guide |
| 433 | Heat Exchanger Overtemperature (EcoBlue) The heat exchanger temperature has exceeded 95°C. This is a more severe overheat condition than… | High | Engineer | View Guide |
| E.01-.04 | Flame Lost 5 Times in 24 Hours (200/400) On Baxi 200/400 boilers, E.01-.04 indicates flame has been lost 5 times within 24 hours… | High | Engineer | View Guide |
| E.02-.07 | No/Low System Water Pressure (200/400) On Baxi 200/400 boilers, E.02-.07 indicates system pressure is below 0.5 bar. | Low | DIY Check | View Guide |
| E.04-.10 | Failure to Light (200/400) On Baxi 200/400 boilers, E.04-.10 indicates the boiler has failed to ignite — possibly a… | Medium | DIY Check | View Guide |
| E.04-.12 | False Flame Signal (200/400) On Baxi 200/400 boilers, E.04-.12 indicates a false flame signal is present — ionisation detected… | High | Engineer | View Guide |
| E0 | Temperature Sensor Fault (Avanta) On Baxi Avanta boilers, E0 indicates a temperature sensor fault. | Medium | Engineer | View Guide |
| E1 | Overheat (Avanta) On Baxi Avanta boilers, E1 indicates the boiler has overheated. Try bleeding radiators first. | High | Engineer | View Guide |
| E10 | Flow NTC Sensor Fault The flow temperature sensor is giving an incorrect reading or has failed. | Medium | Engineer | View Guide |
| E109 | Pre-Heating Circuit Fault A fault has been detected in the pre-heating circuit. This affects the boiler's ability to… | Medium | Engineer | View Guide |
| E11 | Return NTC Sensor Fault The return temperature sensor is giving an incorrect reading or has failed. | Medium | Engineer | View Guide |
| E110 | Boiler Overheat The boiler has reached its maximum safe operating temperature and the safety thermostat has locked… | High | Engineer | View Guide |
| E113 | Condensate Trap/System Blocked The condensate drainage system is blocked. This can occur when the condensate siphon is full… | Medium | DIY Check | View Guide |
| E116 | Flow Temperature Too High The boiler flow temperature has exceeded its maximum safe level, triggering a high-temperature lockout. | High | Engineer | View Guide |
| E117 | Gas Valve Error The gas valve has detected a fault — it may not be opening, closing, or… | High | Engineer | View Guide |
| E118 | Flame Without Demand The boiler is detecting a flame signal when no heat demand exists — a safety-critical… | High | Engineer | View Guide |
| E119 | Low Water Pressure The most common Baxi fault code. System water pressure has dropped below 0.5 bar —… | Low | DIY Check | View Guide |
| E12 | DHW Sensor Fault The domestic hot water temperature sensor has a fault. Relevant on combi boilers. | Medium | Engineer | View Guide |
| E125 | Circulation Fault (Primary) Water is not circulating properly through the primary heating circuit. Usually caused by a faulty… | Medium | Engineer | View Guide |
| E128 | Frequent Flame Failure The boiler has lost its flame 12 times in succession, triggering a safety lockout. | High | Engineer | View Guide |
| E130 | Overheat Thermostat Activated The boiler's safety overheat thermostat has been triggered. The boiler has exceeded its safe operating… | High | Engineer | View Guide |
| E131 | Flue Overheat Lockout The flue temperature has reached an unsafe level, triggering the flue thermostat. | High | Engineer | View Guide |
| E133 | Ignition Failure / Frozen Condensate The boiler has failed to ignite or there is a gas supply fault. In winter,… | Medium | DIY Check | View Guide |
| E134 | Gas Valve Relay Error The gas valve relay has failed or is not responding correctly. The boiler cannot safely… | High | Engineer | View Guide |
| E135 | Airflow Fault / Air Pressure Switch The air pressure switch is not registering correctly, preventing safe ignition. | High | Engineer | View Guide |
| E14 | Flow NTC Open Circuit The flow temperature sensor circuit is broken. | Medium | Engineer | View Guide |
| E15 | Fan Fault The fan is not running at the correct speed or has stopped. | High | Engineer | View Guide |
| E151 | PCB Internal Fault The Printed Circuit Board has detected an internal fault that cannot be reset by the… | High | Engineer | View Guide |
| E154 | Circulation Pump Fault The central heating pump is not running or is not producing sufficient water flow. The… | High | Engineer | View Guide |
| E16 | Air Pressure Switch Open The APS is not closing when the fan runs. | High | Engineer | View Guide |
| E160 | Fan Fault The boiler fan is not operating correctly — it may not be running, running too… | High | Engineer | View Guide |
| E161 | Fan Fault (Secondary) A secondary fan fault — the fan speed sensor or air pressure switch is giving… | High | Engineer | View Guide |
| E164 | Pressure Sensor Fault The water pressure sensor is giving an incorrect or out-of-range reading. | Medium | Engineer | View Guide |
| E167 | PCB Error The Printed Circuit Board has a detected fault (non-lockout version). | Medium | Engineer | View Guide |
| E168 | PCB Fault / Lockout The main Printed Circuit Board has detected an unspecified fault and locked the boiler out.… | High | Engineer | View Guide |
| E169 | Ignition Lockout (After 5 Attempts) The boiler has failed to ignite after 5 attempts and locked out. | Medium | DIY Check | View Guide |
| E17 | Return NTC Open Circuit The return temperature sensor circuit is broken. | Medium | Engineer | View Guide |
| E18 | DHW NTC Open Circuit The hot water sensor circuit is broken. | Medium | Engineer | View Guide |
| E180 | Water Hammer / Circulation Noise Noise from water circulation — kettling, banging or hammering sounds — indicating scale buildup on… | Medium | Engineer | View Guide |
| E19 | Flow NTC Short Circuit The flow NTC wiring has a short circuit. | Medium | Engineer | View Guide |
| E193 | Return Temperature Sensor Fault The return water temperature sensor has a fault in its wiring or has failed. | Medium | Engineer | View Guide |
| E2 | Poor Circulation (Avanta) On Baxi Avanta boilers, E2 indicates poor or no water circulation through the system. | Medium | DIY Check | View Guide |
| E20 | Flame Failure — Lockout The boiler failed to detect a flame after the ignition sequence, or the flame extinguished… | Medium | DIY Check | View Guide |
| E21 | Condensate Blocked The condensate drain is blocked or frozen. | Medium | DIY Check | View Guide |
| E215 | Fan Overspeed The boiler fan is running above its maximum rated speed. Indicates a fault with the… | High | Engineer | View Guide |
| E22 | PCB EEPROM Fault The PCB's internal memory has an error. | High | Engineer | View Guide |
| E220 | Gas Valve Failure to Open The gas valve has received the command to open but has not done so —… | High | Engineer | View Guide |
| E23 | Diverter Valve Fault The diverter valve is stuck or not switching between heating and hot water. | Medium | Engineer | View Guide |
| E24 | Flame Lost During Operation The flame was detected but lost during running. | High | Engineer | View Guide |
| E25 | Rapid Temperature Rise Flow temperature rising faster than safe limits. | High | Engineer | View Guide |
| E26 | Gas Valve Relay Fault The PCB relay for the gas valve has failed. | High | Engineer | View Guide |
| E27 | Pressure Sensor Fault The electronic water pressure sensor is faulty. | Medium | Engineer | View Guide |
| E28 | Frozen Condensate / Flame Failure (Winter) Baxi specifically flags E28 as associated with frozen condensate pipes in winter, making it distinct… | Medium | DIY Check | View Guide |
| E29 | Outdoor Sensor Fault The outdoor temperature sensor is disconnected or faulty. | Low | Engineer | View Guide |
| E3 | PCB Fault (Avanta) On Baxi Avanta boilers, E3 indicates a Printed Circuit Board fault. | High | Engineer | View Guide |
| E30 | eBUS Communication Fault The eBUS communication line has a fault. | Medium | Engineer | View Guide |
| E31 | Frost Protection Active The boiler is running frost protection cycles to prevent freezing. | Medium | DIY Check | View Guide |
| E32 | Flame Detected After Shutdown A flame signal is present when the gas valve should be closed. | High | Engineer | View Guide |
| E33 | Combustion Quality Fault The air/gas mixture is outside the permitted range. | High | Engineer | View Guide |
| E34 | Mains Voltage Fault The mains supply voltage is outside acceptable range. | Medium | Engineer | View Guide |
| E35 | Phase/Neutral Reversed The electrical supply polarity is reversed. | High | Engineer | View Guide |
| E4 | Ignition Failure (Avanta) On Baxi Avanta boilers, E4 indicates ignition failure. | Medium | DIY Check | View Guide |
| E40 | Return Temperature Sensor Fault The return water temperature NTC sensor has developed a fault. It may have an open… | Medium | Engineer | View Guide |
| E50 | Flow Temperature Sensor Fault The flow water temperature NTC sensor has developed a fault. The boiler cannot accurately measure… | Medium | Engineer | View Guide |
| E501 | eBUS/Communication Fault A communication fault between the boiler and a connected external controller (thermostat, zone control, etc.)… | Medium | Engineer | View Guide |
| E53 | Condensate Pipe Frozen / Blocked Baxi's explicit condensate blockage code. Shown when the internal condensate system detects a backup caused… | Medium | DIY Check | View Guide |
| E55 | Fan Speed Fault The fan is running outside its normal speed range — either too fast or too… | High | Engineer | View Guide |
| E78 | Water Pressure Sensor Fault The electronic water pressure sensor is giving an incorrect reading. The boiler cannot verify the… | Medium | Engineer | View Guide |
| E83 | Flow/Return Differential Error The temperature difference between the flow and return is outside the expected range. This usually… | Medium | Engineer | View Guide |
| E84 | Flow/Return Sensor Implausible The flow and return temperature sensors are giving readings that are logically impossible, such as… | Medium | Engineer | View Guide |
| E92 | Combustion Error The combustion quality is outside the permitted range. The air/gas mixture is not correct for… | High | Engineer | View Guide |
| H.01-.05 | Flow/Return Temperature Difference Too High (200/400) On Baxi 200 and 400 series boilers, code H.01-.05 indicates the temperature difference between flow… | Medium | Engineer | View Guide |
| H.01-.08 | Flow Temperature Rising Too Fast (200/400) On Baxi 200/400 boilers, H.01-.08 indicates the flow temperature is increasing too quickly — insufficient… | Medium | Engineer | View Guide |