What to do if your boiler displays a fault code
If your boiler displays a fault code, it's not always something to worry about. It could be a simple fix that you can do yourself, or it may require one of our friendly Glow-worm installers or experts to come out and take a look.
Often, resetting a boiler can resolve a fault or temporarily get your boiler working again.
Looking for your boiler manual? Find it here.
We strongly advise that you do not gain access inside your boiler as this can be dangerous. It’s important that if you smell gas, you need to vacate your property immediately and call the National Gas Emergency Service number on 0800 111 999.
Boiler Fault Codes
F.0
The flow temperature sensor has been interrupted
Possible cause:
- Fault in the electrical connection for the flow temperature sensor
- Flow temperature sensor defective
How to fix it:
- This is a case for a Glow-worm engineer. Don’t try to solve it yourself as opening the boiler casing can be dangerous.
- To solve it please contact our customer service team on 0330 100 3142 or visit myGlow-worm Web to arrange a visit from a Glow-worm engineer.
Often resetting your boiler can resolve a fault or temporarily get your boiler working again.
Clickhere find your user manual which will help you to reset your boiler.
F.1
The return temperature sensor has been interrupted
Possible cause:
- Fault in the electrical connection for the return temperature sensor
- Return temperature sensor defective
How to fix it:
- This is a case for a Glow-worm engineer. Don’t try to solve it yourself as opening the boiler casing can be dangerous.
- To solve it please contact our customer service team on 0330 100 3142 or visit myGlow-worm Web to arrange a visit from a Glow-worm engineer.
Often resetting your boiler can resolve a fault or temporarily get your boiler working again.
Clickhere find your user manual which will help you to reset your boiler.
F.10
The flow temperature sensor has short-circuited
Possible cause:
- Fault in the electrical connection for the flow temperature sensor
- Flow temperature sensor defective
How to fix it:
- This is a case for a Glow-worm engineer. Don’t try to solve it yourself as opening the boiler casing can be dangerous.
- To solve it please contact our customer service team on 0330 100 3142 or visit myGlow-worm Web to arrange a visit from a Glow-worm engineer.
Often resetting your boiler can resolve a fault or temporarily get your boiler working again.
Clickhere find your user manual which will help you to reset your boiler.
F.11
The return temperature sensor has short-circuited
Possible cause:
- Fault in the electrical connection for the return temperature sensor.
- Return temperature sensor defective.
How to fix it:
- This is a case for a Glow-worm engineer. Don’t try to solve it yourself as opening the boiler casing can be dangerous.
- To solve it please contact our customer service team on 0330 100 3142 or visit myGlow-worm Web to arrange a visit from a Glow-worm engineer.
Often resetting your boiler can resolve a fault or temporarily get your boiler working again.
Clickhere find your user manual which will help you to reset your boiler.
F.20
The safety thermal cut out has operated shutting the boiler off
Possible cause:
- System water pressure below normal range of 1 to 1.5 bar
- Fault in the electrical connection for the flow and/or return temperature sensor
- Flow and/or return temperature sensor defective
- Circulation fault, pump, valve, blockage
- Water pressure sensor defective
- Volume flow sensor defective
- Ignition cable, ignition plug or ignition electrode
How to fix it:
- Check the water pressure and refill the system if needed.
- Look for leaks and check the system for any issues.
- Ensure radiator valves are open, and external pumps and zone valves are working correctly.
- Make sure there are no airlocks in the system.
- This is a case for a Glow-worm installer in the first instance, as it can relate to how the boiler is working with the heating system.
Often resetting your boiler can resolve a fault or temporarily get your boiler working again. Find your user manual which will help you to reset your boiler.
To solve it please contact your heating installer or find your nearest installer.
Glow-worm will attend to any fault code, however we reserve the right to charge a call out fee for non-product faults.
F.22
Low water pressure in the system
Possible cause:
- The water pressure in your system is below the normal range of 1 to 1.5 bar
- A problem with the water pressure sensor
- Loose, disconnected, or faulty wiring for the pump or pressure sensor
- Water pressure sensor faulty
- The pump may not be working properly (Open vented boilers only).
- Internal expansion vessel faulty
How to fix it:
If your system water pressure is showing less than 1 bar:
This can be solved without an engineer if you are competent to do so. The following guidance and resources are used at your own risk, Glow-worm accepts no liability as a result.
- Locate your filling loop (Unsure? Download your user manual here)
- Slowly increase the water pressure to be between 1 to 1.5 bar. Find out how to repressurise your Glow-worm boiler here.
If you need further support, please contact our homeowner technical support line on 0344 736 0059.
If your system water pressure is showing more than 1 bar:
- This is a case for a Glow-worm engineer. Don’t try to solve it yourself as opening the boiler casing can be dangerous.
- To solve it please contact our customer service team on 0330 100 3142 or visit myGlow-worm Web to arrange a visit from a Glow-worm engineer.
Often resetting your boiler can resolve a fault or temporarily get your boiler working again. Find your user manual which will help you to reset your boiler.
F.23
The temperature difference between the flow/return pipe is too great
Possible cause:
- Air in the product
- Fault in the electrical connection for the flow and/or return temperature sensor.
- Flow and/or return temperature sensor defective.
- Circulation fault, pump, valve, blockage.
- Internal expansion vessel defective.
How to fix it:
- This is a case for a Glow-worm installer in the first instance, as it can relate to how the boiler is working with the heating system.
- To solve it please contact your heating installer or find your nearest installer.
Often resetting your boiler can resolve a fault or temporarily get your boiler working again. Find your user manual which will help you to reset your boiler.
Glow-worm will attend to any fault code, however we reserve the right to charge a call out fee for non-product faults.
F.24
The temperature increases too quickly
Possible cause:
- Air in the product
- System pressure too low
- Fault in the electrical connection for the flow and/or return temperature sensor
- Flow and/or return temperature sensor defective
- Circulation fault, pump, valve, blockage
- Internal expansion vessel defective
How to fix it:
- If you have an open vented boiler this is likely a case for a Glow-worm installer in the first instance, as it can relate to how the boiler is working with the heating system.
- To solve it please contact your heating installer or find your nearest installer.
- If you have a system or combination boiler this is a case for a Glow-worm engineer. Don’t try to solve it yourself as opening the boiler casing can be dangerous.
- To solve it please contact our customer service team on 0330 100 3142 or visit myGlow-worm Web to arrange a visit from a Glow-worm engineer.
Often resetting your boiler can resolve a fault or temporarily get your boiler working again. Find your user manual which will help you to reset your boiler.
Glow-worm will attend to any fault code, however we reserve the right to charge a call out fee for non-product faults.
F.27
A flame signal has been detected while the burner is off
Possible cause:
- Gas valve not fully closed
- PCB defective
How to fix it:
- This is a case for an expert. Don’t try to solve it yourself as it can be dangerous.
- To solve it please contact our customer service team on 0330 100 3142 or visit myGlow-worm Web to arrange a visit from a Glow-worm engineer.
Often resetting your boiler can resolve a fault or temporarily get your boiler working again. Find your user manual which will help you to reset your boiler
F.28
The boiler has failed to ignite
Possible cause:
- Not enough gas reaching the boiler (for example, low gas pressure or insufficient credit on a pre-payment meter.
- Condensate has backed up in the combustion chamber due to a blocked condensate pipe.
- The ignition electrode may be faulty.
- The PCB (printed circuit board) could be faulty.
- There may be an issue with the flue system.
How to fix it:
- Check if other gas appliances in your home are working.
- If you have a pre-payment gas meter, ensure you have enough credit and top up if needed.
- During cold weather, check for ice blockages in any outdoor condensate pipes.
Watch the video to learn how to defrost your frozen condensate pipe.
Outside of the above, this is a case for a Glow-worm engineer. Don’t try to solve it yourself as opening the boiler casing can be dangerous.
- To solve it please contact our customer service team on 0330 100 3142 or visit myGlow-worm Web to arrange a visit from a Glow-worm engineer.
Often resetting your boiler can resolve a fault or temporarily get your boiler working again. Find your user manual which will help you to reset your boiler.
Glow-worm will attend to any fault code, however we reserve the right to charge a call out fee for non-product faults.
F.29
The flame has gone out and the boiler has failed to reignite
Possible cause:
- The gas supply is interrupted, insufficient gas pressure.
- Fault in the flue gas route caused by recirculation or flue gas blockage.
- Poor electrical earthing.
- Condensate discharge pipe blocked.
- Control electrode got contact with the burner.
How to fix it:
- Check if other gas appliances in your home are working.
- If you have a pre-payment gas meter, ensure you have enough credit and top up if needed.
- During cold weather, check for ice blockages in any outdoor condensate pipes.
Watch the video to learn how to defrost your frozen condensate pipe.
Outside of the above, this is a case for a Glow-worm engineer. Don’t try to solve it yourself as opening the boiler casing can be dangerous.
To solve it please contact our customer service team on 0330 100 3142 or visit myGlow-worm Web to arrange a visit from a Glow-worm engineer.
Often resetting your boiler can resolve a fault or temporarily get your boiler working again. Find your user manual which will help you to reset your boiler.
Glow-worm will attend to any fault code, however we reserve the right to charge a call out fee for non-product faults.
F.32
Fan fault
Possible cause:
- Fan defective.
- Plug or harness defective.
- PCB issue
How to fix it:
- This is a case for a Glow-worm engineer. Don’t try to solve it yourself as opening the boiler casing can be dangerous.
- To solve it please contact our customer service team on 0330 100 3142 or visit myGlow-worm Web to arrange a visit from a Glow-worm engineer.
- Often resetting your boiler can resolve a fault or temporarily get your boiler working again. Find your user manual which will help you to reset your boiler.
F.70
The Device Specific Number (DSN) is incorrect, missing or does not match the coding resistor
Possible cause:
- Device Specific Number not set / is incorrect.
- Interruption in the cable harness.
How to fix it:
This is a case for a Glow-worm engineer. Don’t try to solve it yourself as opening the boiler casing can be dangerous.
To solve it please contact our customer service team on 0330 100 3142 or visit myGlow-worm Web to arrange a visit from a Glow-worm engineer.
Often resetting your boiler can resolve a fault or temporarily get your boiler working again. Find your user manual which will help you to reset your boiler.
F.72
The temperature spread between the flow and return temperature sensor is invalid
Possible cause:
- Flow and/or return temperature sensor defective.
- Circulation fault, pump, valve, blockage.
How to fix it:
This is a case for a Glow-worm installer in the first instance, as it can relate to how the boiler is working with the heating system.
To solve it please contact your heating installer or find your nearest installer.
Often resetting your boiler can resolve a fault or temporarily get your boiler working again. Find your user manual which will help you to reset your boiler.
Glow-worm will attend to any fault code, however we reserve the right to charge a call out fee for non-product faults.
F.75
The pressure change is too low when the heating pump is started up
Possible cause:
- System pressure below normal range of 1 to 1.5 bar
- Air in the product/heating system
- Water pressure sensor defective
- Internal heating pump defective
- Open circuit in cable harness
How to fix it:
If your system water pressure is showing less than 1 bar:
This can be solved without an engineer if you are competent to do so. The following guidance and resources are used at your own risk, Glow-worm accepts no liability as a result.
- Locate your filling loop (Unsure? Download your user manual)
- Slowly increase the water pressure to be between 1 to 1.5 Bar. Watch the video on how to do this here.
- If you need further support, please contact our homeowner technical support line on 0344 736 0059.
If your system water pressure is showing more than 1 bar:
This is a case for a Glow-worm engineer. Don’t try to solve it yourself as opening the boiler casing can be dangerous.
To solve it please contact our customer service team on 0330 100 3142or visit myGlow-worm Web to arrange a visit from a Glow-worm engineer.
Often resetting your boiler can resolve a fault or temporarily get your boiler working again. Find your user manual which will help you to reset your boiler.
F.83
When the burner starts, little or no temperature increase is registered at the flow or return temperature sensor
Possible cause:
- System pressure too low.
- Circulation fault, pump, valve, blockage.
- Flow/return temperature sensor fault.
How to fix it:
This is a case for a Glow-worm installer in the first instance, as it can relate to how the boiler is working with the heating system.
To solve it please contact your heating installer or find your nearest installer.
Often resetting your boiler can resolve a fault or temporarily get your boiler working again. Find your user manual which will help you to reset your boiler.
Glow-worm will attend to any fault code, however we reserve the right to charge a call out fee for non-product faults.
F.84
The temperature differences between the flow and return temperature sensors return implausible values
Possible cause:
- Flow and return pipe work crossed.
- Circulation fault, pump, valve, blockage.
- Flow and return temperature sensors incorrectly fitted or on the wrong pipe.
How to fix it:
This is a case for a Glow-worm installer in the first instance, as it can relate to how the boiler is working with the heating system.
To solve it please contact your heating installer or find your nearest installer.
Often resetting your boiler can resolve a fault or temporarily get your boiler working again. Find your user manual which will help you to reset your boiler.
Glow-worm will attend to any fault code, however we reserve the right to charge a call out fee for non-product faults.
F.88
The electrical connection to the gas valve has been interrupted
Possible cause:
- Gas valve assembly connected incorrectly.
- Short circuit in the cable harness.
How to fix it:
This is a case for a Glow-worm engineer. Don’t try to solve it yourself as opening the boiler casing can be dangerous.
To solve it please contact our customer service team on 0330 100 3142 or visit myGlow-worm Web to arrange a visit from a Glow-worm engineer.
Often resetting your boiler can resolve a fault or temporarily get your boiler working again. Find your user manual which will help you to reset your boiler.
If your fault code isn’t listed above please contact 0344 736 0059 for further assistance
In doubt? Contact our friendly Glow-worm experts
Many boiler faults codes can require a Glow-worm engineer or installer to diagnose the issue and clear the fault. With their expert knowledge they'll be able take care of the issue and hopefully clear the fault code.
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