Low
S.99 on Glow-worm Energy7 Combi

Your boiler is currently running a self-diagnostic check, which is a normal process and does not necessarily indicate a problem.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

What the manual says

Manufacturer manual

Internal automatic test programmes

From this model's manual
Verified against the Glow Worm Energy7 Combi installation & service manual, page 51.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

DIY fix possible

Wait for the boiler to complete its internal cycle, which should take a few minutes.If the code persists, perform a system reset by pressing the reset button on the control panel.If the boiler fails to return to normal operation, switch it off at the mains for 30 seconds and switch it back on.

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