Glow-worm Ultracom sxi Fault codes & diagnostics

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

System Natural Gas 18-30 kW 2007-2012 Discontinued

Replaced by: Ultracom2 sxi

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Fault codes

All 2 documented codes

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ECO

Your boiler is currently set to an energy-saving mode because your hot water temperature has dropped below 50°C, often occurring after a high demand for water.

Low DIY-safe

What to check first

  1. Wait for the boiler to reheat the water cylinder naturally.
  2. Press the 'ECO' button to toggle the mode off if you require hotter water immediately.
  3. Check that the hot water temperature setting on the control panel hasn't been turned down too low.
Full explanation for ECO
F1

Your boiler has detected very cold water in the storage tank and has paused operation as a safety measure to prevent the internal pipes from freezing.

Low DIY-safe £0-60

What to check first

  1. Wait for the house temperature to rise naturally, which will warm the water in the tank.
  2. Ensure any loft hatches are closed and that the boiler area is not exposed to freezing draughts.
  3. The fault should automatically clear once the water temperature inside the unit rises above 10°C.

Parts commonly replaced

  • None (Environmental issue)
  • NTC Temperature Sensor
Full explanation for F1
Status & diagnostic codes

37 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.22 Status Your boiler is performing a routine self-check of the internal pump before it starts the main 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.36 Status Your boiler is working fine, but it is waiting for your thermostat or programmer to tell it to turn on. S.42 Status Your boiler has temporarily stopped heating because an external add-on or control accessory is preventing it from firing up. 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.76 Status Your boiler has temporarily paused operation because it is waiting for a clear reading from the internal water pressure sensor. 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.97 Status Your boiler is temporarily pausing to check the system's water pressure before it starts up to provide heating or hot water. S.98 Status Your boiler is temporarily pausing to check its internal temperature sensors before it starts up again.