Low
d.66 on Glow-worm Ultimate3 Combi

Your boiler is simply indicating that the 'warm start' feature is currently active, which keeps a small amount of water pre-heated so you get hot water faster when you turn on the tap.

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

Activationofthewarmstartfunctionfordomestichotwater

From this model's manual
Verified against the Glow Worm/Glow Worm Ultimate3 Combi installation & service manual, page 43.
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

This is a status code, not a fault, so no repair is required.If you wish to turn this feature off, access your boiler's user menu.Navigate to the 'Warm Start' or 'Comfort' setting and toggle it to 'Off' if you prefer to save energy.

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All 170 fault codes on the Ultimate3 Combi

Seeing a different code? Every code this model can display, in one place.

d.00d.01d.02d.04d.05d.06d.07d.08d.09d.10d.11d.13d.14d.15d.16d.17d.18d.19d.20d.21d.22d.23d.24d.25d.27d.28d.31d.33d.34d.35d.36d.39d.40d.41d.43d.45d.47d.50d.51d.58d.60d.61d.62d.64d.65d.67d.68d.69d.70d.71d.73d.75d.77d.80d.81d.82d.83d.84d.85d.88d.90d.91d.93d.94d.95d.96F.00F.01F.10F.11F.13F.20F.22F.23F.24F.25F.27F.28F.29F.32F.49F.61F.62F.63F.64F.65F.67F.68F.70F.71F.72F.73F.74F.75F.77F.78F.83F.84F.85F.86F.87F.88F.89F.97F2F22Main burner does not lightNeon 1 lit (No)neon 1 not litNeon 2 lit (No)neon 2 not litNeon 3 lit (No)neon 3 not litNeon 4 lit (No)neon 4 not litP.01P.02P.03P.04P.05P.06P.07Pilot does not lightPilot does not stay alightPump OverrunS.0S.01S.02S.03S.04S.05S.06S.07S.08S.10S.11S.13S.14S.15S.16S.17S.20S.21S.22S.23S.24S.25S.26S.27S.28S.30S.31S.32S.33S.34S.39S.41S.42S.46S.53S.54S.88S.91S.96S.97S.98S.99S.108S.109

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