High
90 on Alpha Intec 50CS

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.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

What the manual says

Manufacturer manual

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

From this model's manual
Verified against the Alpha Intec 50cs installation & service manual, page 49.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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