BoilerFaultCodesAlpha 43 Fault Code
The Alpha 43 fault code means: your boiler has lost the signal that confirms a flame is burning, so it has shut down for safety.. It appears on 24 Alpha models in our database.
Technical description: Loss of flame rectification
What causes the Alpha 43 fault?
This fault occurs when the boiler's control board can no longer detect the electrical signal that confirms a flame is present inside the burner. The most common reason is that the sensing probe has become coated in carbon deposits or has worn out, preventing it from 'seeing' the flame even if the boiler has actually ignited. In some cases, it can also be caused by an unstable gas supply or a moisture build-up on the electrical leads.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Alpha models that show the 43 fault code
Click a model for the full fault code list and model-specific repair notes.
- C25 Xtraflame Repair: £150-250
- E-Tec Repair: £120-250
- E-Tec 24 Repair: £120-250
- E-Tec 28 Repair: £120-250
- E-Tec 33 Repair: £120-250
- E-Tec Plus Repair: £120-250
- E-Tec Plus 10 / 18 Repair: £90-250
- E-Tec Plus 24 Repair: £120-250
- E-Tec Plus 28 Repair: £120-250
- E-Tec Plus 33 Repair: £120-250
- E-Tec R Repair: £120-250
- E-Tec Regular Repair: £120-280
- Eco Repair: £150-300
- Eco 11 13 Repair: £120-280
- Evoke Repair: £120-250
- Evoke 10 / 18 Repair: £120-280
- FMK Repair: £120-280
- H25 Xtraflame Repair: £150-250
- Intec 24GS Repair: £150-300
- Intec 28GS Repair: £150-250
- Intec 40GS2 Repair: £150-300
- Intec 50CS Repair: £150-250
- Intec2 25 28XE Repair: £120-250
- Intec2 30SE Repair: £120-250
Source
Alpha 43 fault code information on this page is sourced and cross-checked against the official Alpha service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026