How much does it cost to fix Alpha error code 35?

Typical repair cost for the Alpha 35 fault is £150-300 including labour.

35 High

Alpha 35 Fault Code

Q: What does the Alpha 35 fault code mean?

Your boiler has detected that a specific part of your heating system has reached a dangerously high temperature and has shut itself down to prevent damage.

The Alpha 35 fault code means: your boiler has detected that a specific part of your heating system has reached a dangerously high temperature and has shut itself down to prevent damage.. It appears on 5 Alpha models in our database.

Technical description: Low temperature zone 3 safety thermostat operation

Typical repair cost £150-300 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Alpha models that show the 35 fault code

Click a model for the full fault code list and model-specific repair notes.

240XE Repair: £150-250
C25 Xtraflame Repair: £150-300
H25 Xtraflame Repair: £150-300
Intec 28GS Repair: £150-300
Intec 50CS Repair: £150-300

Source

Alpha 35 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