Glow-worm Flexicom cx Fault codes & diagnostics

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

Combi Natural GasLPG 24-30 kW 2006 onwards Discontinued
GC Numbers 47-047-3347-047-34

Replaced by: Energy Combi

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

The fault code is already on your display

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.
10 High
Versions & GC numbers

Which version do you have?

The GC number on your boiler's data badge identifies the exact appliance and production years, as recorded in the UK Product Characteristics Database.

GC number Appliance (register name) Produced
47-047-33 Flexicom 24cx 2006–present
47-047-34 Flexicom 30cx 2006–present
Just want the most common Glow-worm Flexicom cx faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 10 documented codes

Tap any card for details

F1

Your boiler has stopped working because it cannot light the gas required to provide heat or hot water.

High DIY-safe £100-£350

What to check first

  1. Check if your gas meter has credit and the isolation valve is open
  2. Press the reset button (the flame symbol with a cross) for five seconds
  3. Wait for the boiler to restart and see if the fault clears

Parts commonly replaced

  • Ignition lead
  • Electrode set
  • Gas valve
  • PCB
Full explanation for F1
F4

Your boiler is struggling to keep its flame lit while it tries to heat your home or water, causing it to shut down for safety.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Flue seal
  • Condensate trap

Related codes

Full explanation for F4
F6

Your boiler is struggling to read the temperature of the water flowing through your heating system due to a loose or damaged electrical connection.

High Engineer only £120-200

Parts commonly replaced

  • NTC Sensor
  • Wiring harness

Related codes

Full explanation for F6
F9

Your boiler has stopped because the water pressure inside the heating system has dropped too low.

High DIY-safe £80-150

What to check first

  1. Locate the filling loop (usually a silver braided hose with one or two valves underneath the boiler).
  2. Slowly open the valve(s) to allow mains water into the system until the pressure gauge reads between 1.0 and 1.5 bar.
  3. Close the valve(s) firmly once the correct pressure is reached.

Parts commonly replaced

  • Filling loop
  • Pressure sensor
  • Pressure relief valve

Related codes

Full explanation for F9
F10

Your boiler has lost the signal from one of its internal temperature sensors, causing it to stop heating to prevent potential overheating.

High Engineer only £120-220

Parts commonly replaced

  • Return NTC thermistor
  • Wiring harness

Related codes

Full explanation for F10
F13

Your boiler's internal computer is experiencing an error, meaning it has lost its settings or cannot communicate correctly, causing it to shut down for safety.

High Engineer only £200-350

Parts commonly replaced

  • Main Printed Circuit Board (PCB)
  • Wiring harness

Related codes

Full explanation for F13
F22

Your boiler has stopped working because the water pressure inside the heating system has dropped too low.

High DIY-safe £80-150

What to check first

  1. Locate the filling loop, which is usually a flexible silver hose connected to two valves under the boiler.
  2. Open the valves slowly to allow water into the system until the pressure gauge on the front of the boiler reads between 1.0 and 1.5 bar.
  3. Close both valves tightly and ensure the pressure remains steady.

Parts commonly replaced

  • Filling loop
  • Pressure relief valve
  • Pressure sensor

Related codes

Full explanation for F22
F25

Your boiler is struggling to circulate water properly, causing it to overheat because the heat isn't being moved away from the internal parts fast enough.

High Engineer only £150-350

Parts commonly replaced

  • Central heating pump
  • Plate heat exchanger
  • NTC thermistor sensors

Related codes

Full explanation for F25
F43

Your boiler has detected a communication issue between its internal components, meaning it has safely shut down to prevent incorrect operation.

High Engineer only £150-300

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Wiring harness

Related codes

Full explanation for F43
F70

Your boiler's computer system is having trouble recognising its internal configuration, which prevents it from operating correctly.

High Engineer only £150-300

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • UI Interface Board

Related codes

Full explanation for F70
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 simply resting because your thermostat has reached the desired temperature or the heating is turned off. S.01 Status Your boiler is currently going through a standard starting sequence to clear the air before the burner lights up. S.02 Status Your boiler is simply preparing its internal pump before starting the heating or hot water process. S.03 Status Your boiler is struggling to light the flame correctly, meaning your heating and hot water may not work reliably. S.04 Status Your boiler is operating normally and is currently in the process of heating your water or radiators. S.05 Status Your boiler is simply cooling itself down after finishing a heating or hot water cycle and will restart normally once it has finished. S.06 Status Your boiler is staying in a cooling-down mode because it thinks the internal fan needs to keep running to clear out heat or fumes. S.07 Status Your boiler is briefly running the internal pump after the heating has switched off to cool down the internal components, which is a normal operation and typically not a fault. S.08 Status Your boiler is temporarily pausing its burner to prevent it from switching on and off too frequently, which protects the internal components and saves energy. S.10 Status Your boiler is not showing an error, but is simply indicating that it is currently operating to provide hot water to your taps or shower. S.11 Status Your boiler is performing a routine safety check by running the fan before the burner ignites. S.13 Status Your boiler is struggling to light the burner properly, which is preventing it from heating your water and radiators. S.14 Status Your boiler is currently operating normally in central heating mode and is not experiencing a fault. S.15 Status Your boiler is staying in a cooling-down phase for longer than expected because it is trying to move excess heat away from the internal components. S.16 Status Your boiler is staying in a cooling-down mode because it thinks the air fan is still spinning when it should have stopped. S.17 Status Your boiler is temporarily running the internal pump to cool the system down after it has finished heating your home or water. S.20 Status Your boiler is currently pre-heating a small amount of water to ensure hot water arrives at your taps quickly when you turn them on. S.21 Status Your boiler is currently stuck in a checking stage where the fan is running but the burner has not yet lit. S.22 Status Your boiler is performing a routine self-check of the internal pump before starting the burner to ensure water is circulating correctly. S.23 Status Your boiler is struggling to light because it cannot detect a steady flame after starting up. S.24 Status Your boiler is operating normally and is currently firing the burner to provide heating or hot water; this is a status message, not an error. S.25 Status Your boiler is temporarily running the internal pump or fan to cool itself down after heating your home or water. S.26 Status Your boiler is currently blowing out leftover exhaust gases through the flue, which is a normal process that happens for a short time after you turn off your heating or hot water. S.27 Status Your boiler is temporarily running the pump after the heat has turned off to safely cool down the internal components. S.28 Status Your boiler is taking a short, programmed break to prevent itself from turning on and off too frequently, which protects the components from unnecessary wear. S.30 Status Your boiler is working fine, but it is waiting for a signal from your 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 the central heating has been turned off. S.32 Status Your boiler is temporarily pausing because it thinks it is at risk of freezing or there is a minor airflow issue, and it is waiting for conditions to return to normal. S.34 Status Your boiler has detected very cold temperatures and is running briefly to prevent the internal pipes from freezing. S.36 Status Your boiler is waiting for a signal from your thermostat or timer to turn on, but it isn't receiving one. S.42 Status Your boiler has temporarily stopped providing heating or hot water because an external control or smart accessory is preventing it from firing up. S.53 Status Your boiler has temporarily paused because the water is heating up too quickly or isn't circulating properly through the system. S.54 Status Your boiler has sensed that heat is rising too quickly because there is likely not enough water circulating through the pipes. S.76 Status Your boiler is temporarily paused because it is double-checking the water pressure levels before it continues to run. S.96 Status Your boiler is temporarily pausing to double-check its health sensors before it starts providing heat or hot water. S.97 Status Your boiler is temporarily pausing to check the water pressure levels before it can start your heating or hot water. S.98 Status Your boiler is temporarily pausing to check its temperature sensors before starting up to ensure everything is working correctly.