BoilerFaultCodesAlpha 70 Fault Code
The Alpha 70 fault code means: your boiler has detected a communication error between its internal temperature sensors, which means it cannot safely monitor the water temperature and has shut down as a precaution.. It appears on 15 Alpha models in our database.
Technical description: Return/flow sensorExchange from possible wiring fault
What causes the Alpha 70 fault?
This fault occurs when the boiler's control board receives conflicting or missing data from the internal sensors that monitor water temperature. The most common reason is a physical failure of the thermistor sensors themselves or a loose connection in the wiring harness that links them to the main computer. Because the boiler can no longer verify if the water is at a safe temperature, it shuts down to prevent overheating.
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 70 fault code
Click a model for the full fault code list and model-specific repair notes.
- 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: £120-350
- 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-£200
- E-Tec, E-Tec Plus, Evoke Repair: £90-180
- Evoke Repair: £120-250
- Evoke 10 / 18 Repair: £120-350
- FMK Repair: £120-220
Source
Alpha 70 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