High
15 on Saunier Duval Thelia 23E

Your boiler is having trouble controlling the flow of gas necessary to ignite the flame, meaning it cannot provide heat or hot water.

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

Stepper motor fault (gas valve)

From this model's manual
Verified against the Saunier Duval Thelia 23e installation & service manual, page 37.
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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