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 Code
Possible Cause
F.00
Fault: Flow temperature sensor
F.01
Fault: Return temperature sensor
F.10
Short circuit: Flow temperature sensor
F.11
Short circuit: Return temperature sensor
F.12 and F.91
Short circuit: Cylinder temperature sensor
F.13
Short circuit: Domestic hot water cylinder temperature sensor
F.20
Safety switch-oft. The overheating temperature reached
F.22
Safety switch-oft. Low water pressure in the boiler
F.23
Safety switch-oft. Temperature difference too great (NTC1/NTC2)
F.24
Safety switch-oft. The temperature rises too fast
F.25
Safety switch-off. Flue gas temperature too high
F.27
Safety switch-off. Fault in flame detection
F.28
Fault: Ignition unsuccessful when starting up
F.29
Fault: Flame loss
F.32
Fan frost protection function active: Fan speed outside the tolerance values
F.33
Fan frost protection function active: Air pressure switch fault
Value sent back by ASIC is incorrect (flame slgnal)
F.88
Fault: Unstable flame (analogue input)
F.70
Invalid product code (DSN)
F.71
Fault: Flow/return temperature sensor
F.72
Fault: Deviation in the water pressure sensor/return temperature sensor
F.73
Fault: Water pressure sensor not connected or has short-circuited
F.74
Fault: Electrical problemin the water pressure sensor
F.75
Fault: Pressure sensor
F.78
The safety cut-out in the primary heat exchanger is defective
F.77
Fault: Condensate or smoke
F.78
Interruption to DHW outlet sensor at external controller
F.83
Fault: Burner temperature sensor
F.84
Fault: Flow/return temperature sensor
F.85
Fault: Temperature sensor
F.88
Fault: Underfloor heating contact
F.87
Fault: Electrodes
F.88
Fault: Gas valve
F.89
Fault: Pump
Connection
No communication between the PCB and the user interface
Betacom Range
Fault Code
Possible Cause
Red LED on
Lockout – Low water pressure, Make sure pressure is above 1.5bar, reset boiler
Red LED flashing
DHW temperature control knob in service position – Turn DHW control knob into temperature range
Red LED flashing
Overheat – Check both overheat stats
Yellow LED flashing
Error – 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 on
Flame present on the burner
Green LED on
Boiler ready for operation
Green LED off
No power to the boiler – Check for 230volts into the appliance, check the fuse on pcb
Green LED flashing
Boiler in stand-by – Reset position
Betacom A Range
Fault Code
Possible Cause
F00
Flow heating temperature sensor fault
F01
Return heating temperature sensor fault
F10
Flow heating temperature sensor fault
F11
Return heating temperature sensor fault
F20
Overheating fault
F22
Low water pressure
F23
Water circulation fault
F24
Water circulation fault
F26
Fault in gas valve
F27
Flame detection fault
F28
Ignition fault
F29
Loss of flame during operation
F32
Incorrect air pressure
F49
EBUS voltage fault
F61
Fault in the mainboard
F62
Fault in the mainboard
F63
Fault in the mainboard
F64
Fault in the mainboard
F65
Fault in the mainboard
F67
Fault in the mainboard
F68
Fluctuation of flame signal
F70
User interface incompatible with the mainboard
F71
Flow heating temperature sensor fault
F72
Permanent temperature difference between flow and return heating sensors
F73
Heating circuit pressure sensor fault
F74
Heating circuit pressure sensor fault
F76
Thermal fuse fault
F77
Fault in gas valve motor
F83
No water in the installation
F84
Permanent temperature difference between flow and return heating sensors
F85
Flow and Return heating sensor fault
F86
Underfloor heating contact fault
Err
User interface fault
Betacom C Range
Fault Code
Possible Cause
Temperature 30 flashing
Fault on CH thermistor
Temperature 40 flashing
Fault on DHW thermistor
Temperature 50 flashing
Fault on outside sensor
Temperature 60 flashing
Low system pressure
Temperature 70 flashing
Fault on APS
Temperature 80 flashing
Overheat open circuit
Temperature 90 flashing
Flame or gas failure
Compact E Range
Fault Code
Possible Cause
No DHW
Check dhw microswitch
No C/H
Check the microswitch if dhw demand-led is lit
No C/H but the boiler is firing
Check divertor motor and cartridge
Boiler locks out within 10 seconds
Check pump proving switch, an air pressure switch and overheat stat
Poor burner pressure
Check burner pressure/ignition adjustment pots on PCB
Compact S Range
Fault Code
Possible Cause
No DHW
Check external controls, Please test for 230V on switch live to contact
No C/H
Check external controls, Please test for 230V on switch live contact
No C/H or DHW
Check external controls, Please test for 230V on switch live contact
Boiler locks out within 10 seconds
Check pump proving switch, an air pressure switch and overheat stat
Poor burner pressure
Check burner pressure/ignition adjustment pots on PCB
CI Range Boiler
Fault Code
Possible Cause
F1
Ignition fault
F2
Fan/APS
F4
Ignition fault
F5
Overheat Fault
F6
Central heating flow thermistor
F7
Domestic hot water thermistor
F8
Tank thermistor (N/A For this appliance)
F9
Water pressure sensor fault (please contact GW technical department for further information
F10
Central return flow thermistor
F11
Mainboard connection fault
F12
Connection fault between the main pcb and display pcb
F13
Main pcb connection fault
F14
Central heating flow temperature > 95 degrees
F15
Gas valve stepper motor fault
F16
Flame detection fault
F17
Power supply is less than 170v
F18
User interface fault
F19
Central heating thermistor unplugged
F20
Software incompatibility
CI Plus Range
Fault Code
Possible Cause
F1
Ignition fault
F2
Fan/APS
F3
Air fault
F4
Ignition fault
F5
Overheat Fault
F6
Central heating flow thermistor
F7
Domestic hot water thermistor
F8
Tank thermistor (N/A For this appliance)
F9
Water pressure sensor fault (please contact GW technical department for further information
F10
Central return flow thermistor
F11
Main board connection fault
F12
Connection fault between the main pcb and display pcb
F13
Main pcb connection fault
F14
Central heating flow temperature > 95 degrees
F15
Gas valve stepper motor fault
F16
Flame detection fault
F17
Power supply is less than 170v
F18
User interface fault
F19
Central heating thermistor unplugged
F20
Software incompatibility
CXI Range
Fault Code
Possible Cause
F1
Ignition fault
F2
Fan
F3
Fan unable to reach ignition speed
F4
Ignition fault
F5
Overheat Fault
F6
Central heating flow thermistor
F7
Domestic hot water thermistor
F8
Tank thermistor (N/A For this appliance)
F9
Water pressure sensor fault (please contact GW technical department for further information
F10
Central return flow thermistor
F11
Main board connection fault
F12
Connection fault between main pcb and display pcb
F13
Main pcb connection fault
F14
Central heating flow temperature > 95 degrees
F15
Gas valve stepper motor fault
F16
Flame detection fault
F17
Power supply is less than 170v
F18
User interface fault
F19
Central heating thermistor unplugged
F20
Software incompatibility
F24
Central heating return temperature > 90 degrees
F25
Poor circulation
F26
Poor circulation
Flexicom CX Range
Fault Code
Possible Cause
F1
Ignition fault
F3
Fan unable to reach ignition speed
F4
Ignition fault
F5
Overheat Fault
F6
Central heating flow thermistor
F7
Domestic hot water thermistor
F9
Water pressure sensor fault, blocked flow filter or pump fault
F10
Central return flow thermistor
F11
Flow and or return thermistor fault
F13
PCB memory or sensing fault
F14
Gas valve control defective
F15
E-bus voltage failure
F22
Low water pressure or ignition temperature rise too slow
F24
Central heating return temperature > 90 degrees
F25
Circulation fault
F43
Generic error
F70
Software incompatible
F73
Unable to see pump activate
F77
Condensate pump error (optional)
Flexicom HX Range
Fault Code
Possible Cause
F1
Ignition fault
F3
Fan unable to reach ignition speed
F4
Ignition fault
F5
Overheat Fault
F6
Central heating flow thermistor
F9
Low water pressure Sensor
F10
Central return flow thermistor
F11
Flow and or return thermistor fault
F13
PCB memory or sensing fault
F14
Gas valve control defective
F15
E-bus voltage failure
F22
Low water pressure or ignition temperature rise too slow
F25
Circulation fault
F43
Generic error
F70
Software incompatible
F73
Unable to see pump activate
F77
Condensate pump error (optional)
Flexicom SX Range
Fault Code
Possible Cause
F1
Ignition fault
F3
Fan unable to reach ignition speed
F4
Ignition fault
F5
Overheat Fault
F6
Central heating flow thermistor
F7
Domestic hot water thermistor
F9
Low water pressure Sensor
F10
Central return flow thermistor
F11
Flow and or return thermistor fault
F13
PCB memory or sensing fault
F14
Gas valve control defective
F15
E-bus voltage failure
F22
Low water pressure or ignition temperature rise too slow
F25
Circulation fault
F43
Generic error
F70
Software incompatible
F73
Unable to see pump activate
F77
Condensate pump error (optional)
HXI Range Boiler
Fault Code
Possible Cause
F1
Ignition fault
F2
Fan
F3
Fan unable to reach ignition speed
F4
Ignition fault
F5
Overheat Fault
F6
Central heating flow thermistor
F7
Domestic hot water thermistor
F8
Tank thermistor (N/A For this appliance)
F9
Earlier models only (please contact GW technical department for further information)
F10
Central return flow thermistor
F11
Mainboard connection fault
F12
Connection fault between the main pcb and display pcb
F13
Main pcb connection fault
F14
Central heating flow temperature > 95 degrees
F16
Flame detection fault
F17
Power supply is less than 170v
F18
User interface fault
F19
Central heating thermistor unplugged
F20
Software incompatibility
F24
Central heating return temperature > 90 degrees
F25
Poor circulation
F26
Poor circulation
SI Range Boiler
Fault Code
Possible Cause
F1
Ignition fault
F2
Fan/APS
F4
Ignition fault
F5
Overheat Fault
F6
Central heating flow thermistor
F7
Domestic hot water thermistor
F8
Tank thermistor (N/A For this appliance)
F9
Water pressure sensor fault (please contact GW technical department for further information)
F10
Central return flow thermistor
F11
Mainboard connection fault
F12
Connection fault between the main pcb and display pcb
F13
Main pcb connection fault
F14
Central heating flow temperature > 95 degrees
F15
Gas valve stepper motor fault
F16
Flame detection fault
F17
Power supply is less than 170v
F18
User interface fault
F19
Central heating thermistor unplugged
F20
Software incompatibility
SXI Range Boiler
Fault Code
Possible Cause
F1
Ignition fault
F2
Fan
F3
Fan unable to reach ignition speed
F4
Ignition fault
F5
Overheat Fault
F6
Central heating flow thermistor
F7
Domestic hot water thermistor
F8
Tank thermistor (N/A For this appliance)
F9
Water pressure sensor fault (please contact GW technical department for further information)
F10
Central return flow thermistor
F11
Mainboard connection fault
F12
Connection fault between the main pcb and display pcb
F13
Main pcb connection fault
F14
Central heating flow temperature > 95 degrees
F15
Gas valve stepper motor fault
F16
Flame detection fault
F17
Power supply is less than 170v
F18
User interface fault
F19
Central heating thermistor unplugged
F20
Software incompatibility
F24
Central heating return temperature > 90 degrees
F25
Poor circulation
F26
Poor circulation
Ultracom2 CXI Range
Fault Code
Possible Cause
F00
Flow heating temperature sensor fault
F01
Return heating temperature sensor fault
F10
Flow heating temperature sensor fault
F11
Return heating temperature sensor fault
F20
Overheating fault
F22
Low water pressure
F23
Water circulation fault
F24
Water circulation fault
F26
Fault in gas valve
F27
Flame detection fault
F28
Ignition fault
F29
Loss of flame during operation
F32
Incorrect air pressure
F49
EBUS voltage fault
F61
Fault in the mainboard
F62
Fault in the mainboard
F63
Fault in the mainboard
F64
Fault in the mainboard
F65
Fault in the mainboard
F67
Fault in the mainboard
F68
Fluctuation of flame signal
F70
User interface incompatible with the mainboard
F71
Flow heating temperature sensor fault
F72
Permanent temperature difference between flow and return heating sensors
F73
Heating circuit pressure sensor fault
F74
Heating circuit pressure sensor fault
F76
Thermal fuse fault
F77
Fault in gas valve motor
F83
No water in the installation
F84
Permanent temperature difference between flow and return heating sensors
F85
Flow and Return heating sensor fault
F86
Underfloor heating contact fault
Err
User interface fault
Ultracom2 SXI Range
Fault Code
Possible Cause
F00
Flow heating temperature sensor fault
F01
Return heating temperature sensor fault
F10
Flow heating temperature sensor fault
F11
Return heating temperature sensor fault
F20
Overheating fault
F22
Low water pressure
F23
Water circulation fault
F24
Water circulation fault
F26
Fault in gas valve
F27
Flame detection fault
F28
Ignition fault
F29
Loss of flame during operation
F32
Incorrect air pressure
F49
EBUS voltage fault
F61
Fault in the mainboard
F62
Fault in the mainboard
F63
Fault in the mainboard
F64
Fault in the mainboard
F65
Fault in the mainboard
F67
Fault in the mainboard
F68
Fluctuation of flame signal
F70
User interface incompatible with the mainboard
F71
Flow heating temperature sensor fault
F72
Permanent temperature difference between flow and return heating sensors
F73
Heating circuit pressure sensor fault
F74
Heating circuit pressure sensor fault
F76
Thermal fuse fault
F77
Fault in gas valve motor
F83
No water in the installation
F84
Permanent temperature difference between flow and return heating sensors
F85
Flow and Return heating sensor fault
F86
Underfloor heating contact fault
Err
User interface fault
Ultracom2 35 Store
Fault Code
Possible Cause
F00
Flow heating temperature sensor fault
F01
Return heating temperature sensor fault
F02
Hot water temperature sensor fault
F03
Storage tank temperature sensor fault
F10
Flow heating temperature sensor fault
F11
Return heating temperature sensor fault
F12
Hot water temperature sensor fault
F13
Storage tank temperature sensor fault
F20
Overheating fault
F22
Low water pressure
F23
Water circulation fault
F24
Water circulation fault
F26
Fault in gas valve
F27
Flame detection fault
F28
Ignition fault
F29
Loss of flame during operation
F32
Incorrect air pressure
F49
EBUS voltage fault
F61
Fault in the main board
F62
Fault in the main board
F63
Fault in the main board
F64
Fault in the main board
F65
Fault in the main board
F67
Fault in the main board
F68
Fluctuation of flame signal
F70
User interface incompatible with the main board
F71
Flow heating temperature sensor fault
F72
Permanent temperature difference between flow and return heating sensors
F73
Heating circuit pressure sensor fault
F74
Heating circuit pressure sensor fault
F76
Thermal fuse fault
F77
Fault in gas valve motor
F79
Storage tank temperature sensor fault
F81
Overheating of hot water circuit
F83
No water in the installation
F84
Permanent temperature difference between flow and return heating sensors
F85
Flow and Return heating sensor fault
F86
Underfloor heating contact fault
Err
User interface fault
Ultracom CXI Range
Fault Code
Possible Cause
F1
Ignition fault
F3
Fan unable to reach ignition speed
F4
Ignition fault
F5
Overheat Fault
F6
Central heating flow thermistor
F9
Water pressure sensor fault, blocked flow filter or pump fault
F10
Central return flow thermistor
F11
Main board connection fault
F13
PCB memory or sensing fault
F14
Gas valve control defective
F15
E-bus voltage failure
F22
Low water pressure or ignition temperature rise too slow
F25
Circulation fault
F43
Generic error
F70
Software incompatible
F73
Unable to see pump activate
F77
Condensate pump error (optional)
No display or Er
loose connection X51
Ultracom CX Range
Fault Code
Possible Cause
F1
Ignition fault
F3
Fan unable to reach ignition speed
F4
Ignition fault
F5
Overheat Fault
F6
Central heating flow thermistor
F9
Water pressure sensor fault, blocked flow filter or pump fault
F10
Central return flow thermistor
F11
Main board connection fault
F13
PCB memory or sensing fault
F14
Gas valve control defective
F15
E-bus voltage failure
F22
Low water pressure or ignition temperature rise too slow
F25
Circulation fault
F43
Generic error
F70
Software incompatible
F73
Unable to see pump activate
F77
Condensate pump error (optional)
No display or Er
loose connection X51
Ultracom HXI Range
Fault Code
Possible Cause
F1
Ignition fault
F3
Fan unable to reach ignition speed
F4
Ignition fault
F5
Overheat Fault
F6
Central heating flow thermistor
F9
Water pressure sensor fault, blocked flow filter or pump fault
F10
Central return flow thermistor
F11
Main board connection fault
F13
PCB memory or sensing fault
F14
Gas valve control defective
F15
E-bus voltage failure
F22
Low water pressure or ignition temperature rise too slow
F25
Circulation fault
F43
Generic error
F70
Software incompatible
F73
Unable to see pump activate
F77
Condensate pump error (optional)
No display or Er
loose connection X51
Ultracom SXI Range
Fault Code
Possible Cause
F1
Ignition fault
F3
Fan unable to reach ignition speed
F4
Ignition fault
F5
Overheat Fault
F6
Central heating flow thermistor
F9
Water pressure sensor fault, blocked flow filter or pump fault
F10
Central return flow thermistor
F11
Main board connection fault
F13
PCB memory or sensing fault
F14
Gas valve control defective
F15
E-bus voltage failure
F22
Low water pressure or ignition temperature rise too slow
F25
Circulation fault
F43
Generic error
F70
Software incompatible
F73
Unable to see pump activate
F77
Condensate pump error (optional)
No display or Er
loose connection X51
Ultrapower SXI Range
Fault Code
Possible Cause
F1
Ignition fault
F3
Fan unable to reach ignition speed
F4
Ignition fault
F5
Overheat Fault
F6
Central heating flow thermistor
F9
Water pressure sensor fault, blocked flow filter or pump fault
F10
Central return flow thermistor
F11
Main board connection fault
F13
PCB memory or sensing fault
F14
Gas valve control defective
F15
E-bus voltage failure
F22
Low water pressure or ignition temperature rise too slow
F25
Circulation fault
F43
Generic error
F70
Software incompatible
F73
Unable to see pump activate
F77
Condensate pump error (optional)
No display or Er
loose connection X51
Xtramax HE Range
Fault Code
Possible Cause
F1
Ignition fault
F2
Fan
F3
Fan
F4
Ignition fault
F5
Overheat Fault
F6
Central heating flow thermistor
F7
Domestic hot water thermistor
F8
Tank thermistor
F9
Water pressure sensor fault (please contact GW technical department for further information)
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-wormboiler 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-wormboiler?
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-wormboiler 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-wormboiler?
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-wormboiler?
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.
