BoilerFaultCodesAlpha 70 Fault Code
The Alpha 70 fault code means: your boiler has detected a problem with the sensor that monitors water temperature as it returns from your heating system, causing the unit to stop running for safety.. It appears on 13 Alpha models in our database.
Technical description: Return flow sensor error
What causes the Alpha 70 fault?
This fault occurs when the boiler's internal computer receives an incorrect or missing signal from the sensor that monitors water coming back from your radiators. The most common reason is that the sensor itself has developed an electrical fault or the wiring connecting it to the main control board 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
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A cover plan would handle faults like 70: no call-out fees, no surprise bills.
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Alpha models that show the 70 fault code
Click a model for the full fault code list and model-specific repair notes.
- E-Tec 28 Repair: £120-£250
- E-Tec 33 Repair: £120-£250
- E-Tec NX Repair: £150-250
- E-Tec NXS Repair: £120-220
- E-Tec Plus Repair: £120-250
- E-Tec Plus 10 / 18 Repair: £120-350
- E-Tec Plus 28 Repair: £120-250
- E-Tec Plus 33 Repair: £120-250
- E-Tec Plus NX Repair: £150-250
- E-Tec Regular Repair: £120-£200
- Evoke Repair: £150-250
- Evoke 10 / 18 Repair: £150-250
- Evoke NX Repair: £150-250
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 7 July 2026