Complete reference guide for all Alpha boiler fault codes. Find your error code below for detailed causes and step-by-step solutions. Select your boiler series and locate your fault code.
Listed below are the common Alpha fault codes as described by the boiler manufacturer along with possible causes. Click “View Solution” for detailed step-by-step fixes, DIY tips, and when to call a Gas Safe engineer. Alpha boilers display fault codes differently depending on the model – digital displays show numeric codes while older models use flashing LED lights.
| Fault Code | Possible Cause | Solution |
|---|---|---|
| E1 | Ignition failure – gas supply, electrode, or sensor issue | View Solution → |
| E2 | Overheat boiler lockout – pump or flow problem | View Solution → |
| E3 | High flue temperature – blocked heat exchanger or flue | View Solution → |
| E4 | Gas valve electrical fault | View Solution → |
| E5 | Heating flow sensor fault | View Solution → |
| E6 | DHW sensor fault | View Solution → |
| E8 | Maximum resets reached – check fault history | View Solution → |
| E10 | Low system pressure – check for leaks | View Solution → |
| E12 | Cylinder sensor fault (FlowSmart only) | View Solution → |
| E15 | Internal wiring error | View Solution → |
| E16 | Fan fault – wiring or fan failure | View Solution → |
| E20 | Flame sensing fault | View Solution → |
| E24 | Control panel button fault | View Solution → |
| E25 | Overheat lockout – air in system or blocked flow | View Solution → |
| E27 | Insufficient primary flow | View Solution → |
| E29 | Flue sensor fault | View Solution → |
| E31 | Loss of communication with Alpha Climatic control | View Solution → |
| E37 | Low mains voltage | View Solution → |
| E38 | Loss of flame – check electrode and gas valve | View Solution → |
| E43 | Loss of flame – gas supply or sensor issue | View Solution → |
| E44 | Safety lockout | View Solution → |
| E46 | External sensor intervention | View Solution → |
| E47 | Reduced burner output | View Solution → |
| E51 | Climatic RF communication fault | View Solution → |
| Fault Code | Possible Cause | Solution |
|---|---|---|
| E60 | Pump stuck or electrical pump fault | View Solution → |
| E61 | Air in pump – restricted central heating flow | View Solution → |
| E70 | Return/flow sensor wiring fault | View Solution → |
| E75 | Return sensor fault | View Solution → |
| E76 | Flow sensor fault | View Solution → |
| SR | Service reminder – boiler needs servicing | View Solution → |
| Fault Code | Possible Cause | Solution |
|---|---|---|
| 0A1 | Ignition failure – gas supply or electrode issue | View Solution → |
| 0A2 | Flame detection fault | View Solution → |
| 0A3 | Overheat thermostat lockout | View Solution → |
| 0A5 | Fan speed fault – flue or ventilation problem | View Solution → |
| 0A7 | High flue temperature | View Solution → |
| 0A8 | Flame circuit fault | View Solution → |
| 0A9 | Gas valve electrical error | View Solution → |
| 0A15 | Flow and return sensor anomaly | View Solution → |
| 0A16 | Flow sensor temperature rise incorrect | View Solution → |
| 0A17 | Return sensor temperature rise incorrect | View Solution → |
| 0A18 | Sudden temperature change detected | View Solution → |
| 0A21 | Main PCB fault | View Solution → |
| 0A30 | Flow sensor short circuit | View Solution → |
| 0A31 | Flow sensor out of range | View Solution → |
| 0A37 | Insufficient system flow/pressure (model dependent) | View Solution → |
| 0A43 | Return sensor short circuit | View Solution → |
| 0A44 | Return sensor out of range | View Solution → |
| 0A80 | Flow and return sensor connection fault | View Solution → |
| 0E2 | Flame sensing fault | View Solution → |
| 0E13 | Maximum resets reached – over 5 attempts | View Solution → |
| 0E25 | Main PCB fault | View Solution → |
| 0E33 | Low power supply voltage | View Solution → |
| 0E34 | DHW sensor out of range | View Solution → |
| 0E37 | Insufficient system pressure | View Solution → |
| 0E45 | Flue sensor short circuit | View Solution → |
| 0E46 | Flue sensor out of range | View Solution → |
| 0E81 | Flow and return sensor anomaly | View Solution → |
| 0E98 | Flow and return sensor incorrect value | View Solution → |
| 0E99 | Cascade communication error | View Solution → |
| FE94 | Display PCB fault | View Solution → |
| FE95 | External flow sensor fault | View Solution → |
| FE96 | External sensor fault | View Solution → |
| FE97 | Boiler PCB configuration error | View Solution → |
Note: If your Alpha boiler doesn’t have a digital display, it uses LED lights to indicate faults.
| LED Pattern | Fault | Solution |
|---|---|---|
| No lights | No electricity supply | View Solution → |
| Red A/B illuminated | Burner failed to light | View Solution → |
| Yellow B/C illuminated | Burner is alight (normal) | No action required |
| Red A/B flashing | Overheat thermostat operated | View Solution → |
| Yellow flashing (5 sec) | Power on (normal) | No action required |
| Red A + Yellow B | Blocked flue or fan fault | View Solution → |
| Red A + Red B alternating | Very low system pressure | View Solution → |
| Red A + Yellow B flashing | Pump fault or restricted flow | View Solution → |
| All three flashing | Temperature sensor wiring incorrect | View Solution → |
| Fault Code | Possible Cause | Solution |
|---|---|---|
| E1 | Ignition failure | View Solution → |
| E2 | Overheat boiler lockout | View Solution → |
| E3 | High flue temperature | View Solution → |
| E4 | Gas valve electrical fault | View Solution → |
| E5 | Heating flow sensor fault | View Solution → |
| E6 | Internal wiring error | View Solution → |
| E7 | Chimney sweep function active | View Solution → |
| E8 | Maximum resets reached | View Solution → |
| E12 | Cylinder sensor fault | View Solution → |
| E16 | Fan fault | View Solution → |
| E20 | Flame sensing fault | View Solution → |
| E23 | Heating return sensor fault | View Solution → |
| E24 | Control panel button fault | View Solution → |
| E27 | Insufficient primary flow | View Solution → |
| E29 | Flue sensor fault | View Solution → |
| E31 | Loss of Climatic control communication | View Solution → |
| E37 | Low supply voltage | View Solution → |
| E38 | Loss of flame rectification | View Solution → |
| E43 | Loss of flame – check gas supply | View Solution → |
| E44 | Safety lockout | View Solution → |
| E45 | High temperature difference detected | View Solution → |
| E46 | Optional thermostat intervention | View Solution → |
| E47 | Reduced burner output | View Solution → |
| E49 | Return sensor high temperature | View Solution → |
| E51 | Climatic RF communication fault | View Solution → |
| E70 | Return/flow sensor error | View Solution → |
| E71 | No primary temperature increase | View Solution → |
Most common fault. Usually easy DIY fix by repressurising your system.
Common in winter. Often caused by frozen condensate pipe or gas supply issue.
Requires professional repair. Fan or electrical issue preventing safe operation.
❌ NEVER Attempt DIY:
✅ You CAN Try:
Important: Always contact a Gas Safe engineer for gas-related faults.
Our Gas Safe registered engineers are boiler specialists serving Kent and surrounding areas.
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