BoilerFaultCodes.com

Glow-worm Flexicom 18sx Fault Codes

System Natural Gas 18 kW 2007-2015 Discontinued
GC Number: 41-047-15

Replaced by: Energy 18s

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Most common fault codes

F00
Your boiler has stopped working because it cannot accurately measure the temperature of the water leaving the unit.
Gas Safe engineer required · £90-160
F01
Your boiler has stopped working because a sensor that measures the temperature of the water returning to the unit has developed a fault or disconnected.
Gas Safe engineer required · £90-160
F1
Your boiler has stopped working because it cannot light the gas to start the heating process.
May be DIY safe · £100-£350

All 30 fault codes

Code Severity Plain English
F00 High Your boiler has stopped working because it cannot accurately measure the temperature of the water leaving the unit.
F01 High Your boiler has stopped working because a sensor that measures the temperature of the water returning to the unit has developed a fault or disconnected.
F1 High Your boiler has stopped working because it cannot light the gas to start the heating process.
F10 High Your boiler has stopped working because a sensor that monitors the temperature of the water leaving the unit has failed or disconnected.
F11 High Your boiler has stopped working because a sensor that monitors the temperature of the water returning to the unit has developed an electrical fault.
F13 High Your boiler has lost communication with the temperature sensor on your hot water cylinder, meaning it cannot tell how hot your water is.
F20 High Your boiler has reached an unsafe temperature and has automatically shut down to prevent damage or safety issues.
F22 High Your boiler has detected that there is not enough water pressure in the system to operate safely, which has caused it to shut down.
F23 High Your boiler has sensed that water is not circulating through the system properly, causing a large temperature gap between the pipes leaving and returning to the unit.
F24 High Your boiler is overheating because water isn't moving through the system fast enough, causing it to shut down to prevent damage.
F25 High Your boiler has switched itself off because the waste gases are getting too hot, which is usually caused by a lack of water circulating through the system.
F26 High Your boiler has stopped working because an internal motor that controls the gas flow is not moving as it should.
F27 High Your boiler has stopped working because it cannot confirm that the flame is staying lit safely.
F28 High Your boiler has failed to ignite and is not receiving a steady gas supply or spark, meaning you currently have no heating or hot water.
F29 High Your boiler was running but the flame has unexpectedly gone out, causing the system to stop working as a safety precaution.
F41 High Your boiler has detected an issue with the fan that safely clears exhaust gases, causing the system to shut down for safety.
F42 High Coded resistance fault
F43 High Your boiler's main control unit is confused because a specific internal configuration component is missing or has the wrong electrical profile.
F61 High Your boiler's main control board has suffered a communication failure or internal electrical fault, meaning it can no longer send instructions to heat your home.
F62 High Your boiler's main control board has suffered an internal electronic failure and is unable to manage the heating process safely.
F63 High Your boiler's main internal computer has developed a communication failure, meaning it can no longer control the heating and hot water functions.
F64 High Your boiler's main internal computer has developed a communication or hardware error and cannot manage the heating process safely.
F65 High Your boiler’s internal computer has developed an electronic fault, preventing the system from running safely.
F67 High Your boiler's internal computer has encountered a critical communication error and can no longer control the heating system safely.
F70 High Your boiler's internal control boards are not communicating correctly because they do not recognise each other's software or settings.
F72 High Your boiler has detected that its temperature sensors are giving conflicting readings or have failed, which has caused the system to stop working for safety.
F73 High Your boiler has stopped working because it cannot accurately measure the water pressure due to a sensor or wiring issue.
F74 High Your boiler has lost the ability to monitor its own water pressure, meaning it has shut down as a safety precaution.
F75 High Your boiler is struggling to detect a rise in water pressure when the pump starts, which is preventing it from firing up to provide heating or hot water.
F77 High Your boiler has stopped working because the system that removes waste water is blocked or the pump used to drain it has failed.

Status & diagnostic codes

These codes indicate your boiler's operating state or a diagnostic reading — not necessarily a fault. Status codes (S.) mean normal operation; diagnostic codes (D.) are informational readings used by engineers.

Code Type Description
S.00 Status Your boiler is working perfectly and is simply waiting for a signal from your thermostat or programmer to turn the heating on.
S.01 Status Your boiler is currently preparing its internal fan to safely clear any leftover gases before it begins the ignition process.
S.02 Status Your boiler is simply performing a routine preparation step by running its internal pump before ignition to ensure safe water flow.
S.03 Status Your boiler is failing to light the gas flame properly during its first stage of operation.
S.04 Status Your boiler is operating normally and is currently heating up to provide warmth for your radiators or hot water.
S.05 Status Your boiler is briefly keeping the internal parts running to cool itself down after heating your home or water.
S.06 Status Your boiler is staying in a cooling-down phase for too long because the fan is still running after it should have stopped.
S.07 Status Your boiler is continuing to run the internal pump to cool down the system after the heating has switched off.
S.08 Status Your boiler is taking a short, programmed break to prevent it from turning on and off too frequently, which protects the internal parts from unnecessary wear.
S.30 Status Your boiler is working correctly but is currently waiting for a signal from your room thermostat or programmer to tell it to turn the heating on.
S.31 Status Your boiler is currently set to provide hot water only, and your central heating has been turned off via the controls.
S.32 Status Your boiler has paused its operation because it has detected an issue with the air flow or fan stability while trying to prevent internal freezing.
S.34 Status Your boiler has sensed very cold temperatures and has automatically turned itself on to prevent the internal pipes from freezing.
S.36 Status Your boiler is working correctly, but it is currently sitting in standby because your thermostat or external timer is not telling it to turn on.
S.42 Status Your boiler has temporarily stopped running 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 much hotter than the water returning, suggesting it is struggling to move heat away from its core.
S.54 Status Your boiler has sensed that heat is rising too quickly because there isn't enough water moving through the system to carry the heat away.
S.76 Status Your boiler is temporarily paused because it is waiting for a stable reading from the internal water pressure sensor.
S.96 Status Your boiler is temporarily pausing to test a temperature sensor before it starts up, which is delaying your heating or hot water.
S.97 Status Your boiler is temporarily pausing to check if there is enough water pressure before it starts up, which is preventing your heating and hot water from running.
S.98 Status Your boiler is temporarily pausing to check its temperature sensors before heating your home, which may cause a delay in getting hot water or heating.

Glow-worm Flexicom 18sx is discontinued — time for a new one?

Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.

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