glow worm boiler fault codes error codes with advice solutions
Last updated on: 28 August 2024

Glow-worm boiler fault codes & error codes with advice & solutions

Glow-worm is a major player in the energy sector in the United Kingdom. They began building boilers in Derbyshire in the 1930s and have since grown to become one of the UK’s major providers of sustainable energy solutions. Glow-worm to provide ‘excellent quality, reliability, and durability.

The goal of this blog, however, is to assist you in identifying the issues that your boiler may be experiencing, as well as provide a list of all Glow-worm boiler fault codes and Glow-worm error codes, so that you may feel a bit less anxious about your boiler.

Glow-worm offers a variety of gas boiler models, including combi boilers, system boilers, and ordinary heat-only boilers, in a variety of sizes and styles whichever according to your requirement and need Glow-worm, which began manufacturing boilers in 1934 at the Derwent Foundry in Derbyshire, are dedicated for providing durable and highly efficient boilers to their customers for the past 80 years. Glow-worm was acquired by the Vaillant Group, Europe’s second-largest heating manufacturer, in 2001.

List of Glow Worm Boiler Fault Codes and Error Codes

Fault CodePossible Cause
F.00Fault: Flow temperature sensor
F.01Fault: Return temperature sensor
F.10Short circuit: Flow temperature sensor
F.11Short circuit: Return temperature sensor
F.12 and F.91Short circuit: Cylinder temperature sensor
F.13Short circuit: Domestic hot water cylinder temperature sensor
F.20Safety switch-oft. The overheating temperature reached
F.22Safety switch-oft. Low water pressure in the boiler
F.23Safety switch-oft. Temperature difference too great (NTC1/NTC2)
F.24Safety switch-oft. The temperature rises too fast
F.25Safety switch-off. Flue gas temperature too high
F.27Safety switch-off. Fault in flame detection
F.28Fault: Ignition unsuccessful when starting up
F.29Fault: Flame loss
F.32Fan frost protection function active: Fan speed outside the tolerance values
F.33Fan frost protection function active: Air pressure switch fault
FA9eBUS fault: Voltage too low
F.61Fault: Gas valve control system
F.82Fault: Gas valve switch-off control
F.83Fault: EEPROM
F.64Fault: Electronics/sensor/analogue-to-digital converter
F.85Fault: Electronics temperature too high
F.67Value sent back by ASIC is incorrect (flame slgnal)
F.88Fault: Unstable flame (analogue input)
F.70Invalid product code (DSN)
F.71Fault: Flow/return temperature sensor
F.72Fault: Deviation in the water pressure sensor/return temperature sensor
F.73Fault: Water pressure sensor not connected or has short-circuited
F.74Fault: Electrical problemin the water pressure sensor
F.75Fault: Pressure sensor
F.78The safety cut-out in the primary heat exchanger is defective
F.77Fault: Condensate or smoke
F.78Interruption to DHW outlet sensor at external controller
F.83Fault: Burner temperature sensor
F.84Fault: Flow/return temperature sensor
F.85Fault: Temperature sensor
F.88Fault: Underfloor heating contact
F.87Fault: Electrodes
F.88Fault: Gas valve
F.89Fault: Pump
ConnectionNo communication between the PCB and the user interface

Betacom Range

Fault CodePossible Cause
Red LED onLockout – Low water pressure, Make sure pressure is above 1.5bar, reset boiler
Red LED flashingDHW temperature control knob in service position – Turn DHW control knob into temperature range
Red LED flashingOverheat – Check both overheat stats
Yellow LED flashingError – Wait for a minimum of 30 seconds after turning the DHW control knob into the temperature range and the CH temperature control knob into power (reset position) before turning into either summer or temperature position.
Yellow LED onFlame present on the burner
Green LED onBoiler ready for operation
Green LED offNo power to the boiler – Check for 230volts into the appliance, check the fuse on pcb
Green LED flashingBoiler in stand-by – Reset position

Betacom A Range

Fault CodePossible Cause
F00Flow heating temperature sensor fault
F01Return heating temperature sensor fault
F10Flow heating temperature sensor fault
F11Return heating temperature sensor fault
F20Overheating fault
F22Low water pressure
F23Water circulation fault
F24Water circulation fault
F26Fault in gas valve
F27Flame detection fault
F28Ignition fault
F29Loss of flame during operation
F32Incorrect air pressure
F49EBUS voltage fault
F61Fault in the mainboard
F62Fault in the mainboard
F63Fault in the mainboard
F64Fault in the mainboard
F65Fault in the mainboard
F67Fault in the mainboard
F68Fluctuation of flame signal
F70User interface incompatible with the mainboard
F71Flow heating temperature sensor fault
F72Permanent temperature difference between flow and return heating sensors
F73Heating circuit pressure sensor fault
F74Heating circuit pressure sensor fault
F76Thermal fuse fault
F77Fault in gas valve motor
F83No water in the installation
F84Permanent temperature difference between flow and return heating sensors
F85Flow and Return heating sensor fault
F86Underfloor heating contact fault
ErrUser interface fault

Betacom C Range

Fault CodePossible Cause
Temperature 30 flashingFault on CH thermistor
Temperature 40 flashingFault on DHW thermistor
Temperature 50 flashingFault on outside sensor
Temperature 60 flashingLow system pressure
Temperature 70 flashingFault on APS
Temperature 80 flashingOverheat open circuit
Temperature 90 flashingFlame or gas failure

Compact E Range

Fault CodePossible Cause
No DHWCheck dhw microswitch
No C/HCheck the microswitch if dhw demand-led is lit
No C/H but the boiler is firingCheck divertor motor and cartridge
Boiler locks out within 10 secondsCheck pump proving switch, an air pressure switch and overheat stat
Poor burner pressureCheck burner pressure/ignition adjustment pots on PCB

Compact S Range

Fault CodePossible Cause
No DHWCheck external controls, Please test for 230V on switch live to contact
No C/HCheck external controls, Please test for 230V on switch live contact
No C/H or DHWCheck external controls, Please test for 230V on switch live contact
Boiler locks out within 10 secondsCheck pump proving switch, an air pressure switch and overheat stat
Poor burner pressureCheck burner pressure/ignition adjustment pots on PCB

CI Range Boiler

Fault CodePossible Cause
F1Ignition fault
F2Fan/APS
F4Ignition fault
F5Overheat Fault
F6Central heating flow thermistor
F7Domestic hot water thermistor
F8Tank thermistor (N/A For this appliance)
F9Water pressure sensor fault (please contact GW technical department for further information
F10Central return flow thermistor
F11Mainboard connection fault
F12Connection fault between the main pcb and display pcb
F13Main pcb connection fault
F14Central heating flow temperature > 95 degrees
F15Gas valve stepper motor fault
F16Flame detection fault
F17Power supply is less than 170v
F18User interface fault
F19Central heating thermistor unplugged
F20Software incompatibility

CI Plus Range

Fault CodePossible Cause
F1Ignition fault
F2Fan/APS
F3Air fault
F4Ignition fault
F5Overheat Fault
F6Central heating flow thermistor
F7Domestic hot water thermistor
F8Tank thermistor (N/A For this appliance)
F9Water pressure sensor fault (please contact GW technical department for further information
F10Central return flow thermistor
F11Main board connection fault
F12Connection fault between the main pcb and display pcb
F13Main pcb connection fault
F14Central heating flow temperature > 95 degrees
F15Gas valve stepper motor fault
F16Flame detection fault
F17Power supply is less than 170v
F18User interface fault
F19Central heating thermistor unplugged
F20Software incompatibility

CXI Range

Fault CodePossible Cause
F1Ignition fault
F2Fan
F3Fan unable to reach ignition speed
F4Ignition fault
F5Overheat Fault
F6Central heating flow thermistor
F7Domestic hot water thermistor
F8Tank thermistor (N/A For this appliance)
F9Water pressure sensor fault (please contact GW technical department for further information
F10Central return flow thermistor
F11Main board connection fault
F12Connection fault between main pcb and display pcb
F13Main pcb connection fault
F14Central heating flow temperature > 95 degrees
F15Gas valve stepper motor fault
F16Flame detection fault
F17Power supply is less than 170v
F18User interface fault
F19Central heating thermistor unplugged
F20Software incompatibility
F24Central heating return temperature > 90 degrees
F25Poor circulation
F26Poor circulation

Flexicom CX Range

Fault CodePossible Cause
F1Ignition fault
F3Fan unable to reach ignition speed
F4Ignition fault
F5Overheat Fault
F6Central heating flow thermistor
F7Domestic hot water thermistor
F9Water pressure sensor fault, blocked flow filter or pump fault
F10Central return flow thermistor
F11Flow and or return thermistor fault
F13PCB memory or sensing fault
F14Gas valve control defective
F15E-bus voltage failure
F22Low water pressure or ignition temperature rise too slow
F24Central heating return temperature > 90 degrees
F25Circulation fault
F43Generic error
F70Software incompatible
F73Unable to see pump activate
F77Condensate pump error (optional)

Flexicom HX Range

Fault CodePossible Cause
F1Ignition fault
F3Fan unable to reach ignition speed
F4Ignition fault
F5Overheat Fault
F6Central heating flow thermistor
F9Low water pressure Sensor
F10Central return flow thermistor
F11Flow and or return thermistor fault
F13PCB memory or sensing fault
F14Gas valve control defective
F15E-bus voltage failure
F22Low water pressure or ignition temperature rise too slow
F25Circulation fault
F43Generic error
F70Software incompatible
F73Unable to see pump activate
F77Condensate pump error (optional)

Flexicom SX Range

Fault CodePossible Cause
F1Ignition fault
F3Fan unable to reach ignition speed
F4Ignition fault
F5Overheat Fault
F6Central heating flow thermistor
F7Domestic hot water thermistor
F9Low water pressure Sensor
F10Central return flow thermistor
F11Flow and or return thermistor fault
F13PCB memory or sensing fault
F14Gas valve control defective
F15E-bus voltage failure
F22Low water pressure or ignition temperature rise too slow
F25Circulation fault
F43Generic error
F70Software incompatible
F73Unable to see pump activate
F77Condensate pump error (optional)

HXI Range Boiler

Fault CodePossible Cause
F1Ignition fault
F2Fan
F3Fan unable to reach ignition speed
F4Ignition fault
F5Overheat Fault
F6Central heating flow thermistor
F7Domestic hot water thermistor
F8Tank thermistor (N/A For this appliance)
F9Earlier models only (please contact GW technical department for further information)
F10Central return flow thermistor
F11Mainboard connection fault
F12Connection fault between the main pcb and display pcb
F13Main pcb connection fault
F14Central heating flow temperature > 95 degrees
F16Flame detection fault
F17Power supply is less than 170v
F18User interface fault
F19Central heating thermistor unplugged
F20Software incompatibility
F24Central heating return temperature > 90 degrees
F25Poor circulation
F26Poor circulation

SI Range Boiler

Fault CodePossible Cause
F1Ignition fault
F2Fan/APS
F4Ignition fault
F5Overheat Fault
F6Central heating flow thermistor
F7Domestic hot water thermistor
F8Tank thermistor (N/A For this appliance)
F9Water pressure sensor fault (please contact GW technical department for further information)
F10Central return flow thermistor
F11Mainboard connection fault
F12Connection fault between the main pcb and display pcb
F13Main pcb connection fault
F14Central heating flow temperature > 95 degrees
F15Gas valve stepper motor fault
F16Flame detection fault
F17Power supply is less than 170v
F18User interface fault
F19Central heating thermistor unplugged
F20Software incompatibility

SXI Range Boiler

Fault CodePossible Cause
F1Ignition fault
F2Fan
F3Fan unable to reach ignition speed
F4Ignition fault
F5Overheat Fault
F6Central heating flow thermistor
F7Domestic hot water thermistor
F8Tank thermistor (N/A For this appliance)
F9Water pressure sensor fault (please contact GW technical department for further information)
F10Central return flow thermistor
F11Mainboard connection fault
F12Connection fault between the main pcb and display pcb
F13Main pcb connection fault
F14Central heating flow temperature > 95 degrees
F15Gas valve stepper motor fault
F16Flame detection fault
F17Power supply is less than 170v
F18User interface fault
F19Central heating thermistor unplugged
F20Software incompatibility
F24Central heating return temperature > 90 degrees
F25Poor circulation
F26Poor circulation

Ultracom2 CXI Range

Fault CodePossible Cause
F00Flow heating temperature sensor fault
F01Return heating temperature sensor fault
F10Flow heating temperature sensor fault
F11Return heating temperature sensor fault
F20Overheating fault
F22Low water pressure
F23Water circulation fault
F24Water circulation fault
F26Fault in gas valve
F27Flame detection fault
F28Ignition fault
F29Loss of flame during operation
F32Incorrect air pressure
F49EBUS voltage fault
F61Fault in the mainboard
F62Fault in the mainboard
F63Fault in the mainboard
F64Fault in the mainboard
F65Fault in the mainboard
F67Fault in the mainboard
F68Fluctuation of flame signal
F70User interface incompatible with the mainboard
F71Flow heating temperature sensor fault
F72Permanent temperature difference between flow and return heating sensors
F73Heating circuit pressure sensor fault
F74Heating circuit pressure sensor fault
F76Thermal fuse fault
F77Fault in gas valve motor
F83No water in the installation
F84Permanent temperature difference between flow and return heating sensors
F85Flow and Return heating sensor fault
F86Underfloor heating contact fault
ErrUser interface fault

Ultracom2 SXI Range

Fault CodePossible Cause
F00Flow heating temperature sensor fault
F01Return heating temperature sensor fault
F10Flow heating temperature sensor fault
F11Return heating temperature sensor fault
F20Overheating fault
F22Low water pressure
F23Water circulation fault
F24Water circulation fault
F26Fault in gas valve
F27Flame detection fault
F28Ignition fault
F29Loss of flame during operation
F32Incorrect air pressure
F49EBUS voltage fault
F61Fault in the mainboard
F62Fault in the mainboard
F63Fault in the mainboard
F64Fault in the mainboard
F65Fault in the mainboard
F67Fault in the mainboard
F68Fluctuation of flame signal
F70User interface incompatible with the mainboard
F71Flow heating temperature sensor fault
F72Permanent temperature difference between flow and return heating sensors
F73Heating circuit pressure sensor fault
F74Heating circuit pressure sensor fault
F76Thermal fuse fault
F77Fault in gas valve motor
F83No water in the installation
F84Permanent temperature difference between flow and return heating sensors
F85Flow and Return heating sensor fault
F86Underfloor heating contact fault
ErrUser interface fault

Ultracom2 35 Store

Fault CodePossible Cause
F00Flow heating temperature sensor fault
F01Return heating temperature sensor fault
F02Hot water temperature sensor fault
F03Storage tank temperature sensor fault
F10Flow heating temperature sensor fault
F11Return heating temperature sensor fault
F12Hot water temperature sensor fault
F13Storage tank temperature sensor fault
F20Overheating fault
F22Low water pressure
F23Water circulation fault
F24Water circulation fault
F26Fault in gas valve
F27Flame detection fault
F28Ignition fault
F29Loss of flame during operation
F32Incorrect air pressure
F49EBUS voltage fault
F61Fault in the main board
F62Fault in the main board
F63Fault in the main board
F64Fault in the main board
F65Fault in the main board
F67Fault in the main board
F68Fluctuation of flame signal
F70User interface incompatible with the main board
F71Flow heating temperature sensor fault
F72Permanent temperature difference between flow and return heating sensors
F73Heating circuit pressure sensor fault
F74Heating circuit pressure sensor fault
F76Thermal fuse fault
F77Fault in gas valve motor
F79Storage tank temperature sensor fault
F81Overheating of hot water circuit
F83No water in the installation
F84Permanent temperature difference between flow and return heating sensors
F85Flow and Return heating sensor fault
F86Underfloor heating contact fault
ErrUser interface fault

Ultracom CXI Range

Fault CodePossible Cause
F1Ignition fault
F3Fan unable to reach ignition speed
F4Ignition fault
F5Overheat Fault
F6Central heating flow thermistor
F9Water pressure sensor fault, blocked flow filter or pump fault
F10Central return flow thermistor
F11Main board connection fault
F13PCB memory or sensing fault
F14Gas valve control defective
F15E-bus voltage failure
F22Low water pressure or ignition temperature rise too slow
F25Circulation fault
F43Generic error
F70Software incompatible
F73Unable to see pump activate
F77Condensate pump error (optional)
No display or Erloose connection X51

Ultracom CX Range

Fault CodePossible Cause
F1Ignition fault
F3Fan unable to reach ignition speed
F4Ignition fault
F5Overheat Fault
F6Central heating flow thermistor
F9Water pressure sensor fault, blocked flow filter or pump fault
F10Central return flow thermistor
F11Main board connection fault
F13PCB memory or sensing fault
F14Gas valve control defective
F15E-bus voltage failure
F22Low water pressure or ignition temperature rise too slow
F25Circulation fault
F43Generic error
F70Software incompatible
F73Unable to see pump activate
F77Condensate pump error (optional)
No display or Erloose connection X51

Ultracom HXI Range

Fault CodePossible Cause
F1Ignition fault
F3Fan unable to reach ignition speed
F4Ignition fault
F5Overheat Fault
F6Central heating flow thermistor
F9Water pressure sensor fault, blocked flow filter or pump fault
F10Central return flow thermistor
F11Main board connection fault
F13PCB memory or sensing fault
F14Gas valve control defective
F15E-bus voltage failure
F22Low water pressure or ignition temperature rise too slow
F25Circulation fault
F43Generic error
F70Software incompatible
F73Unable to see pump activate
F77Condensate pump error (optional)
No display or Erloose connection X51

Ultracom SXI Range

Fault CodePossible Cause
F1Ignition fault
F3Fan unable to reach ignition speed
F4Ignition fault
F5Overheat Fault
F6Central heating flow thermistor
F9Water pressure sensor fault, blocked flow filter or pump fault
F10Central return flow thermistor
F11Main board connection fault
F13PCB memory or sensing fault
F14Gas valve control defective
F15E-bus voltage failure
F22Low water pressure or ignition temperature rise too slow
F25Circulation fault
F43Generic error
F70Software incompatible
F73Unable to see pump activate
F77Condensate pump error (optional)
No display or Erloose connection X51

Ultrapower SXI Range

Fault CodePossible Cause
F1Ignition fault
F3Fan unable to reach ignition speed
F4Ignition fault
F5Overheat Fault
F6Central heating flow thermistor
F9Water pressure sensor fault, blocked flow filter or pump fault
F10Central return flow thermistor
F11Main board connection fault
F13PCB memory or sensing fault
F14Gas valve control defective
F15E-bus voltage failure
F22Low water pressure or ignition temperature rise too slow
F25Circulation fault
F43Generic error
F70Software incompatible
F73Unable to see pump activate
F77Condensate pump error (optional)
No display or Erloose connection X51

Xtramax HE Range

Fault CodePossible Cause
F1Ignition fault
F2Fan
F3Fan
F4Ignition fault
F5Overheat Fault
F6Central heating flow thermistor
F7Domestic hot water thermistor
F8Tank thermistor
F9Water pressure sensor fault (please contact GW technical department for further information)
F10Central return flow thermistor
F11Main board connection fault
F12User interface connection fault
F13PCB memory or sensing fault
F14Gas valve control defective
F16Flame detection fault
F17Power supply is less than 170v
F18User interface fault
F19Central heating thermistor unplugged
F20Software incompatibility
F23Water circulation fault
F24Cental heating return temperature > 90 degrees
F25Maximum temperature rise slope
F26Maximum delta temperature

Xtrafast 96/120 Range

Fault CodePossible Cause
F00No-fault
F02Air flow fault
F04Ignition fault – flame detection
F05Overheating
F06Central heating thermistor/wiring fault
F07Domestic hot water thermistor/wiring fault
F08Storage vessel thermistor/wiring fault
F09System pressure sensor fault
F10Fan fault
F11Poor circulation
F12User interface fault
F13Main pcb fault
F14Central heating flow temperature > 97 degrees
F15Gas mechanism fault
F20Communication fault

Xtrafast 96/120E1 Range

Fault CodePossible Cause
F00No fault
F02Air flow fault
F04Ignition fault – flame detection
F05Overheating
F06Central heating thermistor/wiring fault
F07Domestic hot water thermistor/wiring fault
F08Storage vessel thermistor/wiring fault
F09System pressure sensor fault
F10Fan fault
F11Poor circulation
F12User interface fault
F13Main pcb fault
F14Central heating flow temperature > 97 degrees
F15Gas mechanism fault
F20Communication fault

Glow-worm boiler fault codes

Read more about List Of Worcester Bosch Boiler Error Codes With Effective Solutions

FAQs

What is the f5 fault code Glow-worm boiler?

The Glow-worm boiler fault code f5 occurs when your boiler enters overheat status, it could be due to previous work, such as airlocks in your central heating system. To prevent the boiler from tripping out, ensure sure there is no air in the central heating system.

What does the f1 error code on a Glow-worm boiler mean?

If the F1 fault code appears on your Glow-worm boiler, it signifies there was a problem with the ignition sequence. There are a number of ignition problems that might cause your boiler to cease working.

Fault codes on Glow-worm boilers will assist your engineer in determining the source of the problem faster than if they were to start from zero. When a fault code appears on the display panel, your boiler will most likely lockout. It won’t operate again until your boiler repair firm has identified the issue.

What is the f22 fault code Glow-worm boiler?

Low pressure is indicated by the F22 boiler trouble code. There’s a strong probability you have a leak if this just appeared on the screen and your boiler is dropping pressure. Otherwise, the system is likely to have an airlock.

What is the f3 fault code on Glow-worm boiler?

Fan unable to attain ignition speed’ is an F3 code on a Glow-worm Boiler. If your Glow-worm Boiler is giving you the F3 signal, it’s possible that the fan is functioning but not at full speed. This can happen if the boiler’s mechanical side is malfunctioning or if a temperamental loose wire is present.

What is Glow-worm boiler f4 fault code?

A small blockage caused the F4 fault codes, which were quickly and easily resolved. There was also no need to get a Gas Safe registered professional to solve the problem because it was not related to the gas boiler.

How do I reset my Glow-worm boiler?

Fault codes beginning with the letter F are shown on glow-worm boilers to indicate defects. Simply push the reset button and wait 5 seconds to restart a Glow-worm boiler. You should be able to observe your boiler come back to life.

What does F75 mean on a Glow-worm boiler?

The F75 code indicates that the boiler failed to perceive a rise in system pressure when it tried to spin the pump during its start-up checks.

Posted by: Martin Astley 08 March 2022