BoilerFaultCodesAlpha 23 Fault Code
The Alpha 23 fault code means: your boiler has detected a problem with the sensor that monitors the temperature of the water returning from your radiators.. It appears on 21 Alpha models in our database.
Technical description: Heating return sensor fault
What causes the Alpha 23 fault?
This fault occurs when the boiler's control board receives an incorrect or missing signal from the sensor that measures the temperature of the water coming back from your radiators. The most common reason is that the internal components of the sensor have failed due to age, or the electrical wiring connecting the sensor to the main computer has become loose or damaged.
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 23 fault code
Click a model for the full fault code list and model-specific repair notes.
- 240XE Repair: £150-300
- C25 Xtraflame Repair: £120-220
- E-Tec Repair: £150-250
- E-Tec 24 Repair: £150-250
- E-Tec 28 Repair: £150-250
- E-Tec 33 Repair: £150-250
- E-Tec Plus Repair: £120-250
- E-Tec Plus 10 / 18 Repair: £100-180
- 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: £120-220
- E-Tec Regular Repair: £90-160
- Evoke Repair: £150-250
- Evoke 10 / 18 Repair: £90-160
- FMK Repair: £100-180
- H25 Xtraflame Repair: £120-220
- Intec 28GS Repair: £120-220
- Intec 50CS Repair: £120-220
- Intec2 25 28XE Repair: £120-250
- Intec2 30SE Repair: £120-250
Source
Alpha 23 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