BoilerFaultCodes 00
Your boiler is operating normally and there are no faults currently detected by the system.
Glow-worm Xtrafast 96 120 Fault codes & diagnostics
23 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
Combi Natural Gas 35-37 kW 2001-present
GC Number 47-047-25
Download the Glow-worm Xtrafast 96 120 manual
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Severity at a glance
Each cell = one fault code. Hover to identify. 1 Emergency
20 High
1 Medium
1 Low
Just want the most common Glow-worm Xtrafast 96 120 faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes
All 23 documented codes
Tap any card for details
0 bar Your boiler has lost its water pressure, which means it has stopped running to protect the internal components from damage.
Your boiler has lost its water pressure, which means it has stopped running to protect the internal components from damage.
What to check first
- Locate the filling loop (usually a silver flexible hose) under the boiler.
- Slowly open the one or two small taps on the hose until you hear water flowing.
- Watch the pressure gauge until it reaches between 1.0 and 1.5 bar, then close the taps tightly.
Parts commonly replaced
- Filling loop
- Expansion vessel
- Pressure relief valve
Related codes
02 Your boiler has stopped working because the fan system cannot properly clear waste gases or bring in fresh air to burn fuel safely.
Your boiler has stopped working because the fan system cannot properly clear waste gases or bring in fresh air to burn fuel safely.
Parts commonly replaced
- Fan motor
- Air pressure switch
- Venture tube
Related codes
04 Your boiler is failing to light the flame needed to heat your water and radiators.
Your boiler is failing to light the flame needed to heat your water and radiators.
What to check first
- Check that your gas pre-payment meter hasn't run out of credit
- Ensure other gas appliances in your home, like a hob, are receiving gas
- Press the 'Reset' button on the boiler control panel to see if it restarts
Parts commonly replaced
- Ignition Electrode
- Flame Sensing Electrode
- Gas Valve
Related codes
05 Your boiler has got too hot and has shut itself down as a safety precaution to prevent damage.
Your boiler has got too hot and has shut itself down as a safety precaution to prevent damage.
What to check first
- Check that all radiator valves are fully open (especially TRVs)
- Ensure there is enough water pressure in the system (typically 1.0 to 1.5 bar)
- Press the reset button once the boiler has had time to cool down
Parts commonly replaced
- Overheat Thermostat
- Circulation Pump
- Main Heat Exchanger
Related codes
06 Your boiler has detected a problem with the internal sensor that monitors the temperature of your heating water, meaning the system cannot run safely.
Your boiler has detected a problem with the internal sensor that monitors the temperature of your heating water, meaning the system cannot run safely.
Parts commonly replaced
- Central heating NTC thermistor
- Wiring harness connectors
Related codes
07 Your boiler has stopped providing hot water because the internal sensor responsible for measuring water temperature has either failed or has a loose connection.
Your boiler has stopped providing hot water because the internal sensor responsible for measuring water temperature has either failed or has a loose connection.
Parts commonly replaced
- DHW Thermistor (NTC Sensor)
- Wiring Harness
Related codes
08 Your boiler has lost its ability to monitor the temperature of the stored hot water, meaning it cannot heat your water reliably or safely.
Your boiler has lost its ability to monitor the temperature of the stored hot water, meaning it cannot heat your water reliably or safely.
Parts commonly replaced
- Storage vessel NTC thermistor
- Wiring harness
Related codes
09 Your boiler's internal sensor is struggling to accurately read the water pressure, which prevents the system from operating safely.
Your boiler's internal sensor is struggling to accurately read the water pressure, which prevents the system from operating safely.
Parts commonly replaced
- System pressure sensor
- Sensor wiring harness
Related codes
10 Your boiler has detected that the fan, which safely removes waste gases from the appliance, is not spinning correctly or has lost communication with the main control board.
Your boiler has detected that the fan, which safely removes waste gases from the appliance, is not spinning correctly or has lost communication with the main control board.
Parts commonly replaced
- Fan motor assembly
- Main PCB
- Air pressure switch
Related codes
Showing 11–20 of 23
12 Your boiler's control panel and its internal computer are having trouble communicating with each other, preventing the unit from starting.
Your boiler's control panel and its internal computer are having trouble communicating with each other, preventing the unit from starting.
Parts commonly replaced
- User Interface PCB
- Main Control PCB
- Connection Wiring Loom
13 Your boiler's internal computer has developed a fault and can no longer control the system safely.
Your boiler's internal computer has developed a fault and can no longer control the system safely.
Parts commonly replaced
- Main PCB (Printed Circuit Board)
- Wiring Harness
Related codes
14 Your boiler has shut down because a sensor has detected that it is getting far too hot, likely due to a circulation problem.
Your boiler has shut down because a sensor has detected that it is getting far too hot, likely due to a circulation problem.
Parts commonly replaced
- Circulation Pump
- Flow NTC Sensor
- Main Heat Exchanger
Related codes
15 Your boiler is unable to correctly control the supply of gas it needs to create a flame, causing the system to shut down for safety.
Your boiler is unable to correctly control the supply of gas it needs to create a flame, causing the system to shut down for safety.
Parts commonly replaced
- Gas Valve
- Printed Circuit Board (PCB)
- Wiring Harness
Related codes
16 Your boiler has detected that gas is leaking through its internal safety valves, meaning the system is potentially unsafe and must be shut down immediately.
Your boiler has detected that gas is leaking through its internal safety valves, meaning the system is potentially unsafe and must be shut down immediately.
Parts commonly replaced
- Gas valve
- Gas valve solenoid
- PCB
Related codes
17 Your boiler is struggling because the electricity supply it is receiving is weaker than the level it needs to operate safely.
Your boiler is struggling because the electricity supply it is receiving is weaker than the level it needs to operate safely.
Parts commonly replaced
- Main printed circuit board
- Transformer
Related codes
20 Your boiler's internal computer parts are struggling to talk to each other, which prevents the system from starting up normally.
Your boiler's internal computer parts are struggling to talk to each other, which prevents the system from starting up normally.
Parts commonly replaced
- Main PCB
- User Interface Display PCB
- Wiring Harness
Related codes
21 Your boiler has detected that there is not enough water pressure inside the system to operate safely.
Your boiler has detected that there is not enough water pressure inside the system to operate safely.
What to check first
- Locate the filling loop (usually a silver braided hose with one or two valves) located underneath your boiler.
- Slowly open the valve(s) to allow water to enter the system while watching the pressure gauge on the front of the boiler.
- Close the valve(s) firmly once the needle reaches 1.5 bar, then check the boiler display to see if the fault has cleared.
Parts commonly replaced
- Filling loop
- Pressure relief valve
- Pressure sensor
F0 Your boiler has stopped working because the water pressure is too low for the system to run safely.
Your boiler has stopped working because the water pressure is too low for the system to run safely.
What to check first
- Locate the filling loop (usually a silver flexible hose) underneath the boiler.
- Slowly open the one or two taps/levers on the filling loop to allow water into the system.
- Watch the pressure gauge until it reaches between 1.0 and 1.5 bar, then close the taps fully.
Parts commonly replaced
- Filling loop
- Pressure sensor
- Expansion vessel
Related codes
F9 Your boiler has detected an issue with how it monitors water levels, meaning it cannot confirm there is enough water to safely provide heating or hot water.
Your boiler has detected an issue with how it monitors water levels, meaning it cannot confirm there is enough water to safely provide heating or hot water.
Parts commonly replaced
- Water pressure sensor
- Pressure sensor wiring loom
- Main PCB
Related codes
Showing 21–23 of 23
F12 Your boiler's control panel and its internal computer are failing to talk to each other, meaning the unit cannot receive instructions to operate.
Your boiler's control panel and its internal computer are failing to talk to each other, meaning the unit cannot receive instructions to operate.
Parts commonly replaced
- User Interface PCB
- Main Control PCB
- Wiring harness
Related codes
Pictogram of a spark Your boiler is failing to light because it isn't receiving a gas supply or cannot detect a flame.
Your boiler is failing to light because it isn't receiving a gas supply or cannot detect a flame.
What to check first
- Check that your gas emergency control valve (usually by the meter) is in the 'on' position.
- If you have a pre-payment meter, check that you have sufficient credit.
- Check if other gas appliances in the home, such as a hob, are working correctly.
- Press and hold the reset button for five seconds to see if the boiler restarts.
Parts commonly replaced
- Gas Valve
- Ignition Electrode
- PCB
Related codes
Telephone symbol Your boiler has detected an internal error that prevents it from operating normally, and it requires a professional to identify the specific issue.
Your boiler has detected an internal error that prevents it from operating normally, and it requires a professional to identify the specific issue.
Parts commonly replaced
- Main PCB
- Pressure Sensor
- NTC Thermistor
Related codes
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