BoilerFaultCodes d.94
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Glow-worm Ultracom 35 Store Fault codes & diagnostics
45 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
Combi Natural Gas 35 kW 2007-2013 Discontinued
GC Number 47-019-15
Replaced by: Flexicom
Download the Glow-worm Ultracom 35 Store manual
PDF
Versions & GC numbers
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. 28 High
1 Medium
16 Unrated
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 |
|---|---|---|
| 47-019-15 | Ultracom 2 35 Store | 2011–present |
Appliance names and production years are taken from the UK Product Characteristics Database (the SAP/SEDBUK register). Where a GC number is also printed in this model's own manufacturer manual, both sources were checked to agree.
Just want the most common Glow-worm Ultracom 35 Store faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes
All 45 documented codes
Tap any card for details
Err
User interface fault; Defective user interface
F00 Your boiler has stopped working because it cannot correctly measure the temperature of the water leaving the unit.
Your boiler has stopped working because it cannot correctly measure the temperature of the water leaving the unit.
Parts commonly replaced
- Flow NTC thermistor
- Wiring harness
Related codes
F01 Your boiler has stopped working because a sensor that monitors the temperature of the water returning from your radiators has developed a fault.
Your boiler has stopped working because a sensor that monitors the temperature of the water returning from your radiators has developed a fault.
Parts commonly replaced
- Return thermistor (NTC sensor)
- Wiring harness connecting sensor to PCB
Related codes
F1 Your boiler has failed to ignite and has shut itself down for safety, meaning you will not have any heating or hot water until it is reset or repaired.
Your boiler has failed to ignite and has shut itself down for safety, meaning you will not have any heating or hot water until it is reset or repaired.
What to check first
- Check if your gas meter has credit and other gas appliances like the hob are working
- Press the Reset button (indicated by a flame with a cross through it) for five seconds
- Ensure the boiler pressure gauge is between 1.0 and 1.5 bar
- If it is freezing outside, check that your white plastic condensate pipe hasn't frozen
Parts commonly replaced
- Ignition Electrode
- Gas Valve
- Printed Circuit Board (PCB)
- Spark Lead
Related codes
F02
Hot water temperature sensor fault
F03
Storage tank temperature sensor fault
F3 Your boiler has detected that the internal fan responsible for safely venting exhaust gases is not operating correctly, so it has shut itself down to keep your home safe.
Your boiler has detected that the internal fan responsible for safely venting exhaust gases is not operating correctly, so it has shut itself down to keep your home safe.
Parts commonly replaced
- Fan assembly
- Printed Circuit Board (PCB)
- Wiring harness
Related codes
F10 Your boiler has detected a problem with the sensor that measures the temperature of the water leaving the unit, causing it to shut down as a safety precaution.
Your boiler has detected a problem with the sensor that measures the temperature of the water leaving the unit, causing it to shut down as a safety precaution.
Parts commonly replaced
- Flow NTC thermistor
- Wiring harness
- Main PCB
Related codes
F11 Your boiler has detected an issue with the sensor that monitors the temperature of the water coming back from your radiators, preventing it from heating your home safely.
Your boiler has detected an issue with the sensor that monitors the temperature of the water coming back from your radiators, preventing it from heating your home safely.
Parts commonly replaced
- Return heating thermistor (NTC sensor)
- Thermistor wiring harness
Related codes
Showing 11–20 of 45
F12 Your boiler has lost communication with the sensor that monitors the temperature of your hot water cylinder, meaning it cannot heat your water correctly.
Your boiler has lost communication with the sensor that monitors the temperature of your hot water cylinder, meaning it cannot heat your water correctly.
Parts commonly replaced
- NTC Cylinder Thermistor
- Wiring Harness
- PCB
Related codes
F13 Your boiler's hot water sensor has developed a technical fault, preventing the system from accurately measuring and heating your water.
Your boiler's hot water sensor has developed a technical fault, preventing the system from accurately measuring and heating your water.
Parts commonly replaced
- DHW Thermistor (NTC Sensor)
- Wiring harness connector
F20 Your boiler has switched itself off to prevent damage because the internal water temperature has become too hot.
Your boiler has switched itself off to prevent damage because the internal water temperature has become too hot.
What to check first
- Check that all radiator valves are fully open to allow water to circulate
- Ensure the boiler pressure is between 1 and 1.5 bar on the digital display
- Wait for the boiler to cool down and press the 'Reset' button (flame symbol)
Parts commonly replaced
- Circulation pump
- Overheat thermostat (limit stat)
- Main heat exchanger (flushing service)
Related codes
F22 Your boiler has detected that the water pressure is too low to operate safely and has shut down to prevent damage.
Your boiler has detected that the water pressure is too low to operate safely and has shut down to prevent damage.
What to check first
- Locate the filling loop (usually a silver flexible hose) underneath the boiler.
- Open the one or two small valves on the hose until you hear water flowing.
- Watch the pressure gauge and close the valves when the needle reaches 1.5 bar.
Parts commonly replaced
- Filling loop valve
- Pressure sensor
- Expansion vessel
Related codes
F23 Your boiler has stopped working because the water isn't moving through the system fast enough, causing the internal temperature to rise too quickly.
Your boiler has stopped working because the water isn't moving through the system fast enough, causing the internal temperature to rise too quickly.
What to check first
- Check that all radiator valves are fully open
- Ensure the boiler pressure is between 1.0 and 1.5 bar
- Bleed all radiators to remove trapped air from the system
Parts commonly replaced
- Circulation pump
- Flow/Return thermistors
- Main heat exchanger (flushing service)
Related codes
F24 Your boiler is heating up too quickly because water isn't flowing through the system properly, causing it to shut down to prevent overheating.
Your boiler is heating up too quickly because water isn't flowing through the system properly, causing it to shut down to prevent overheating.
What to check first
- Check that your boiler pressure is between 1.0 and 1.5 bar on the digital display.
- Ensure all radiator valves and isolation valves under the boiler are fully open.
- Bleed your radiators to remove any trapped air pockets that might be blocking flow.
Parts commonly replaced
- Pump
- Main Heat Exchanger
- Flow/Return Thermistors
Related codes
F26 Your boiler has detected a problem with how gas is flowing into the system, which means it cannot light safely and has shut down as a precaution.
Your boiler has detected a problem with how gas is flowing into the system, which means it cannot light safely and has shut down as a precaution.
Parts commonly replaced
- Gas valve
- Main PCB (Printed Circuit Board)
- Wiring harness
Related codes
F27 Your boiler has sensed a flame when there shouldn't be one, or the sensor that monitors the fire is sending a confusing signal to the control board.
Your boiler has sensed a flame when there shouldn't be one, or the sensor that monitors the fire is sending a confusing signal to the control board.
Parts commonly replaced
- Ionisation electrode
- Flame sensing lead
- Printed Circuit Board (PCB)
- Gas valve
Related codes
F28 Your boiler is failing to light the gas flame, which means your heating and hot water will not work until the system is reset or repaired.
Your boiler is failing to light the gas flame, which means your heating and hot water will not work until the system is reset or repaired.
What to check first
- Check that your gas emergency control valve is in the 'on' position.
- If you have a pre-payment gas meter, ensure you have sufficient credit.
- Press the reset button (indicated by a flame with a line through it) for five seconds.
Parts commonly replaced
- Ignition Electrode
- Gas Valve
- Printed Circuit Board (PCB)
- Spark Generator
Related codes
F29 Your boiler has lit successfully but then lost its flame while it was running, causing the system to shut down for safety.
Your boiler has lit successfully but then lost its flame while it was running, causing the system to shut down for safety.
What to check first
- Check that your gas emergency control valve is fully open and you have credit on your meter.
- Verify if other gas appliances in your home, such as a hob, are working correctly.
- Gently press the reset button (indicated by a flame with a line through it) to see if the system restarts.
Parts commonly replaced
- Ignition electrode
- Flame sensing probe
- Gas valve
- Condensate trap (if blocked)
Related codes
Showing 21–30 of 45
F32
Incorrect air pressure
F49 Your boiler has lost communication with its external controls like your thermostat because there is an electrical problem with the wiring connecting them.
Your boiler has lost communication with its external controls like your thermostat because there is an electrical problem with the wiring connecting them.
Parts commonly replaced
- External thermostat/programmer wiring
- eBUS connection block
- Main Printed Circuit Board (PCB)
Related codes
F61 Your boiler has detected an internal communication failure between the main control board and the gas valve, meaning it cannot safely light the flame.
Your boiler has detected an internal communication failure between the main control board and the gas valve, meaning it cannot safely light the flame.
Parts commonly replaced
- Main PCB
- Gas Valve
- Wiring Harness
Related codes
F62 Your boiler has detected an internal electronics failure that prevents it from safely controlling the gas supply, meaning it has shut down for safety.
Your boiler has detected an internal electronics failure that prevents it from safely controlling the gas supply, meaning it has shut down for safety.
Parts commonly replaced
- Main PCB
- Gas Valve
Related codes
F63 Your boiler's internal computer brain has developed a memory error and can no longer process its instructions correctly.
Your boiler's internal computer brain has developed a memory error and can no longer process its instructions correctly.
Parts commonly replaced
- Main PCB (Printed Circuit Board)
Related codes
F64 Your boiler’s internal computer brains are struggling to talk to each other, meaning the system cannot run safely.
Your boiler’s internal computer brains are struggling to talk to each other, meaning the system cannot run safely.
Parts commonly replaced
- Main PCB
- Display PCB
- Wiring harness
Related codes
F65 Your boiler's internal computer boards are having trouble communicating with each other, preventing the system from starting up.
Your boiler's internal computer boards are having trouble communicating with each other, preventing the system from starting up.
Parts commonly replaced
- Main PCB
- User Interface Display PCB
- PCB Wiring Harness
Related codes
F67 Your boiler's internal computer boards have stopped communicating correctly, meaning the system cannot process commands or operate safely.
Your boiler's internal computer boards have stopped communicating correctly, meaning the system cannot process commands or operate safely.
Parts commonly replaced
- Main PCB
- Display PCB
- Wiring Loom
Related codes
F68
Fluctuation of flame signal
F70 Your boiler's main control board has lost communication with its internal identity chip, effectively meaning the boiler has forgotten which model it is and cannot operate.
Your boiler's main control board has lost communication with its internal identity chip, effectively meaning the boiler has forgotten which model it is and cannot operate.
Parts commonly replaced
- Main Printed Circuit Board (PCB)
- DSN (Device Specific Number) Chip
Related codes
Showing 31–40 of 45
F71
Flow heating temperature sensor fault; Flow heating temperature sensor unclipped or defective (no temperature variation)
F72 Your boiler is struggling to accurately measure the water temperature, causing it to shut down to prevent overheating.
Your boiler is struggling to accurately measure the water temperature, causing it to shut down to prevent overheating.
Parts commonly replaced
- Flow NTC thermistor
- Return NTC thermistor
- Wiring harness
Related codes
F73 Your boiler is struggling to read its own water level because of an electrical sensor issue, which has caused it to stop working as a safety precaution.
Your boiler is struggling to read its own water level because of an electrical sensor issue, which has caused it to stop working as a safety precaution.
Parts commonly replaced
- Water pressure sensor
- Wiring harness / lead
- Main PCB
Related codes
F74 Your boiler is having trouble measuring how much water is inside the system, which is causing it to stop running for safety.
Your boiler is having trouble measuring how much water is inside the system, which is causing it to stop running for safety.
Parts commonly replaced
- Water Pressure Sensor
- Wiring Harness
Related codes
F76
Thermal fuse fault; Thermal fuse disconnected; Defective thermal fuse
F77 Your boiler has detected an issue with the system that removes waste water or measured a temperature imbalance, causing it to shut down as a safety precaution.
Your boiler has detected an issue with the system that removes waste water or measured a temperature imbalance, causing it to shut down as a safety precaution.
Parts commonly replaced
- Condensate pump
- Flue gas thermistor
- Wiring harness
Related codes
F79
Storage tank temperature sensor fault; Storage tank temperature sensor fault
F81 Your boiler is struggling to heat up water for your taps because the internal pump or sensor that manages hot water is not working correctly.
Your boiler is struggling to heat up water for your taps because the internal pump or sensor that manages hot water is not working correctly.
Parts commonly replaced
- DHW pump
- Plate heat exchanger
- NTC thermistor
- Internal pipework (de-scaling)
Related codes
F83
No water in the installation : the temperature does not increase when the burner is lit; Return water valve closed; Pump disconnected; Leak in the installation
F84
Permanent temperature difference between flow and return heating sensors; Inverted or disconnected flow and return heating temperature sensors; Defective temperature sensors
Showing 41–45 of 45
F85
Flow and return heating sensors fault; Flow and return heating temperature sensor connected to same tube
F86
Underfloor heating contact fault; Floor heating contact open; Sensor disconnected or defective
P.05
Filling the appliance
P.06
Venting the installation
P.07
Venting the appliance
Status & diagnostic codes 25 operating states & engineer diagnostics
Not faults — these are normal operating states. Tap to expand.
25 operating states & engineer diagnostics
Not faults — these are normal operating states. Tap to expand.
S.00 Status Your boiler is working correctly and is currently in standby mode because your thermostat has reached the desired temperature or the heating timer is off. S.01 Status Your boiler is preparing to start the heating process by running the internal fan to clear out the combustion chamber. S.02 Status Your boiler is performing a routine start-up check by running the internal pump for a few moments before lighting the burner. S.03 Status Your boiler is currently attempting to light the flame but is failing to do so, meaning you won't have heating or hot water until it succeeds. S.04 Status Your boiler is working normally and is currently firing up to provide hot water for your taps or showers. S.05 Status Your boiler is temporarily cooling itself down after finishing a heating or hot water cycle, which is a normal part of its operation. S.06 Status Your boiler's fan is continuing to run after it should have stopped, causing the system to pause for safety reasons. S.07 Status Your boiler is continuing to run its internal water pump after the heating or hot water has been turned off to safely cool down the heat exchanger. S.08 Status Your boiler is taking a short, programmed break to prevent it from turning on and off too frequently, which helps save energy and protect its internal parts. S.20 Status Your boiler is temporarily pre-heating the internal water to ensure you get hot water quickly when you turn on a tap. S.21 Status Your boiler is performing a routine start-up check by running its internal fan before lighting the burner. S.23 Status Your boiler is currently struggling to light the flame it needs to provide heating and hot water. S.24 Status Your boiler is operating normally; this is a status message indicating that the burner is currently lit and heating your water. S.25 Status Your boiler is staying in a cooling-down mode because it thinks the internal temperature is still too high after the heating or hot water has turned off. S.26 Status Your boiler's fan is staying on longer than it should after the heating or hot water has been turned off. S.27 Status Your boiler is continuing to run the pump for a short period after the heating has switched off to safely move excess heat away from the internal components. S.28 Status Your boiler is taking a short, programmed break to prevent it from turning on and off too frequently, which protects the internal parts from unnecessary wear. S.30 Status Your boiler is working fine but hasn't started the heating because your external thermostat or timer is currently telling it to stay off. S.31 Status Your boiler is currently set to provide hot water only, and the central heating has been disabled because it is in summer mode. S.32 Status Your boiler has temporarily paused operation because it has detected very cold temperatures or an unusual fluctuation in the fan speed, often caused by strong winds or a blocked flue. S.34 Status Your boiler is not broken; it has simply noticed the temperature is very low and is running briefly to prevent the internal pipes from freezing. S.53 Status Your boiler has temporarily paused because the water temperature is rising too quickly or unevenly, suggesting a circulation issue or a sensor fault. S.54 Status Your boiler has sensed that there isn't enough water moving through the system to heat up safely, so it has shut down to protect itself. S.96 Status Your boiler is temporarily pausing to perform a routine check on its internal temperature sensors before it can provide heating or hot water. S.98 Status Your boiler is temporarily pausing because it has detected a suspicious temperature difference and is double-checking that its heat sensors are working correctly before it continues.