Low
P.04 on Glow-worm Sustain 12s

Your boiler is currently running a temporary, high-power test cycle and should return to normal operation automatically within 15 minutes.

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

Maximum output function: If there is a hot water request, the product runs in hot water handling mode with maximum heat input. If there is no hot water request, the product runs in heating mode with the heating partial load that is set using diagnostics code d.00. The function is activated for 15 minutes.

From this model's manual
Verified against the Glow Worm Sustain 12s installation & service manual, page 28.
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 fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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