How much does it cost to fix Alpha error code 90?

Typical repair cost for the Alpha 90 fault is £120-250 including labour.

90 High

Alpha 90 Fault Code

Q: What does the Alpha 90 fault code mean?

Your boiler has detected an abnormal reading from the flame sensor, meaning it cannot safely determine if the burner is operating correctly and has shut down as a precaution.

The Alpha 90 fault code means: your boiler has detected an abnormal reading from the flame sensor, meaning it cannot safely determine if the burner is operating correctly and has shut down as a precaution.. It appears on 10 Alpha models in our database.

Technical description: Flame signal beyond limit - The flame signal is beyond the adjustment range required for an extended period of time

Typical repair cost £120-250 (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 90 fault code

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

Source

Alpha 90 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