Glow-worm Ultracom 2 SXI Fault codes & diagnostics

43 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.

Combi Natural Gas 30-38 kW 2007-present

Download the Glow-worm Ultracom 2 SXI manual The official installation & service manual (PDF) — the exact document these fault codes were verified against. PDF

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Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →

Severity at a glance

Each cell = one fault code. Hover to identify.

1 High 42 Unrated

Just want the most common Glow-worm Ultracom 2 SXI faults?

The top 6 problems in plain English — with causes, DIY checks and repair costs.

Fault codes

All 43 documented codes

Tap any card for details

Parts commonly replaced

Ignition lead
Ignition electrode
Gas valve
PCB

Related codes

F4
F13

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Status & diagnostic codes

32 operating states & engineer diagnostics

Not faults — these are normal operating states. Tap to expand.

S.00 Status Your boiler is working correctly and is currently in standby mode because your thermostat or timer is not telling it to provide any heat. S.01 Status Your boiler is currently preparing itself for ignition and checking that the safety fan is working correctly. S.02 Status Your boiler is undergoing a brief, normal startup process where the internal pump circulates water before the burner ignites. S.03 Status Your boiler is currently struggling to light the flame needed to provide you with heating and hot water. S.04 Status Your boiler is operating normally and is currently heating up to provide warmth or hot water. S.05 Status Your boiler is continuing to run its internal fan or pump for a short period to safely cool down after the heating or hot water has been turned off. S.06 Status Your boiler's fan is staying on for longer than it should after the heating has switched off. S.07 Status Your boiler is continuing to circulate water after it has finished heating to help the system cool down safely. S.08 Status Your boiler is taking a short, planned break to prevent the system from turning on and off too frequently, which protects the internal components and saves energy. S.10 Status Your boiler is currently working to heat your hot water tank and this status code is just a normal operational message rather than a fault. S.11 Status Your boiler is performing a routine safety check by starting the fan before the burner ignites. S.13 Status Your boiler is struggling to light the gas flame and is currently stuck in the ignition phase. S.14 Status Your boiler is currently firing up and running as it should to provide heating or hot water, so this is a status message rather than a fault. S.15 Status Your boiler is currently cooling itself down after finishing a heating or hot water cycle, which is a normal operating state rather than a permanent failure. S.16 Status Your boiler is performing a routine cooling cycle to clear internal gases after a burst of activity and is not currently in a fault state. S.17 Status Your boiler is continuing to circulate water after the heating or hot water has been turned off to safely dissipate excess heat. S.20 Status Your boiler is temporarily heating the internal tank to ensure hot water is ready for use, which is a normal operating status rather than a fault. S.21 Status Your boiler is performing a routine check of the internal fan system before it begins the heating process. S.23 Status Your boiler is struggling to light because it is stuck in a cycle of checking for water flow before the ignition process starts. S.24 Status Your boiler is currently operating normally and the burner is lit to provide heat or hot water. S.25 Status Your boiler is currently cooling itself down after use and hasn't yet finished its normal internal checkout process. S.26 Status Your boiler's internal cooling fan is staying on longer than expected after the heating has switched off. S.27 Status Your boiler is continuing to run the internal pump to cool down after use, which is a normal process, but it may be taking longer than usual or indicating an internal circulation issue. S.28 Status Your boiler is taking a short, programmed break to prevent it from turning on and off too frequently, which helps protect the internal components from wear and tear. S.30 Status Your boiler is working correctly, but it is currently waiting for a signal from your room thermostat or programmer to tell it to turn on the heating. S.31 Status Your boiler is currently in summer mode, which means it will provide hot water but has temporarily disabled your central heating. S.32 Status Your boiler has paused operation because its built-in frost protection has been triggered or the fan is struggling to maintain a steady speed in very cold or windy conditions. S.34 Status Your boiler has sensed that the temperature inside is very low and has automatically turned on to prevent the water from freezing and damaging the pipes. S.53 Status Your boiler has temporarily paused because the water leaving the unit is getting much hotter than the water returning, suggesting a circulation problem. S.54 Status Your boiler has sensed that heat is building up too quickly because there is not enough water circulating through the system. S.96 Status Your boiler is briefly pausing to check its temperature sensors before it starts up, which is a normal self-test process. S.98 Status Your boiler is temporarily pausing to check its internal temperature sensors before it starts up again.

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