Glow-worm Energy Fault codes & diagnostics

41 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.

Combi Natural Gas 25-35 kW 2015 onwards Discontinued
GC Numbers 47-019-2447-019-2547-019-26

Replaced by: Energy7 Combi

Download the Glow-worm Energy manual The official installation & service manual (PDF) — the exact document these fault codes were verified against. PDF

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Severity at a glance

Each cell = one fault code. Hover to identify.
2 Emergency 36 High 3 Medium

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
47-019-24 Energy 25c 2015–present
47-019-25 Energy 30c 2015–present
47-019-26 Energy 35c 2015–present

All 41 documented codes

Tap any card for details

Connection

Your boiler's electronic control board is currently failing to 'talk' to the display screen, meaning it cannot receive commands or provide status updates.

High Engineer only £150-300

Parts commonly replaced

  • User Interface PCB
  • Main Control PCB
  • Wiring harness

Related codes

F.00

Your boiler has lost the ability to accurately measure the temperature of the water flowing through the system, so it has shut down as a precaution to prevent overheating.

High Engineer only £120-220

Parts commonly replaced

  • NTC Temperature Sensor
  • Wiring harness

Related codes

F.01

Your boiler has stopped working because it is unable to accurately measure the temperature of the water returning to the system.

High Engineer only £120-220

Parts commonly replaced

  • Return NTC thermistor

Related codes

F.10

Your boiler has detected a faulty connection in its temperature-monitoring system and has safely shut down to prevent overheating.

High Engineer only £120-220

Parts commonly replaced

  • NTC flow temperature sensor
  • Wiring harness

Related codes

F.11

Your boiler has detected a faulty connection in the part that measures the temperature of the water returning to the system, causing the boiler to shut down as a precaution.

High Engineer only £120-200

Parts commonly replaced

  • Return temperature sensor
  • Wiring harness

Related codes

F.13

Your boiler has lost the ability to detect the temperature of your hot water tank because a wire or sensor has stopped communicating correctly.

Medium Engineer only £120-220

Parts commonly replaced

  • DHW cylinder temperature sensor
  • Wiring harness

Related codes

F.20

Your boiler has automatically turned itself off because it has detected that its internal water temperature has become dangerously high.

High Engineer only £150-300

Parts commonly replaced

  • NTC Temperature Sensor
  • Pump
  • Heat Exchanger

Related codes

F.22

Your boiler has stopped working because the amount of water circulating inside your heating system is currently too low.

High DIY-safe £80-120

What to check first

  1. Locate the filling loop, which is a silver braided flexible hose with one or two valves attached under the boiler.
  2. Open the valves slowly to allow mains water into the system until the pressure gauge on the front display reaches between 1.0 and 1.5 bar.
  3. Close the valves tightly and turn the boiler off and on again to clear the error.

Parts commonly replaced

  • Filling loop
  • Pressure relief valve
  • Pressure sensor

Related codes

F.23

Your boiler has shut down because it detected that the water is getting much hotter in one part of the system than in another, suggesting a blockage or a faulty pump.

High Engineer only £150-350

Parts commonly replaced

  • Central heating pump
  • NTC thermistors
  • System filter

Related codes

F.24

Your boiler has detected that the water inside is heating up too quickly, so it has shut itself down to prevent any damage.

High Engineer only £150-300

Parts commonly replaced

  • Central heating pump
  • System filter
  • Heat exchanger blockages

Related codes

Showing 11–20 of 41
F.25

Your boiler has detected that the gases it is producing are getting too hot, so it has safely shut itself down to prevent internal damage.

High Engineer only £150-350

Parts commonly replaced

  • NTC Sensor
  • Heat exchanger
  • Flue system components

Related codes

F.27

Your boiler has stopped working because it cannot confirm that the internal burner flame has lit correctly, so it has shut down for your safety.

High Engineer only £150-300

Parts commonly replaced

  • Flame rectification electrode
  • Ignition lead
  • Printed Circuit Board (PCB)

Related codes

F.28

Your boiler is failing to light the fuel inside, meaning it cannot produce any heating or hot water for your home.

High Engineer only £150-350

Parts commonly replaced

  • Ignition lead
  • Ignition electrode
  • Gas valve
  • Printed Circuit Board (PCB)

Related codes

F.29

Your boiler is attempting to light but is failing to stay on, meaning it cannot provide you with heating or hot water.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Condensate trap

Related codes

F.32

Your boiler has detected that the fan, which pushes waste gases safely outside, is not spinning at the correct speed, likely due to cold weather conditions or a mechanical issue.

High Engineer only £150-300

Parts commonly replaced

  • Fan unit
  • PCB
  • Wiring harness

Related codes

F.33

Your boiler has detected an issue with the airflow system which is preventing it from starting safely.

High Engineer only £150-300

Parts commonly replaced

  • Air pressure switch
  • Fan assembly
  • Venturi

Related codes

F.49

Your boiler is having a communication problem with its internal controls because the electrical signal between them is too weak.

High Engineer only £150-300

Parts commonly replaced

  • eBUS PCB
  • Wiring harness
  • External controls

Related codes

F.61

Your boiler has detected a communication issue with the part that controls the flow of gas, and it has stopped working for your safety.

High Engineer only £150-300

Parts commonly replaced

  • Gas valve
  • Wiring harness
  • Main PCB

Related codes

F.62

Your boiler has detected an issue with the safety mechanism that controls the gas supply, so it has shut itself down to prevent any risk.

Emergency Engineer only £180-350

Parts commonly replaced

  • Gas valve
  • Printed Circuit Board (PCB)
  • Wiring harness

Related codes

F.63

Your boiler's internal computer has encountered a permanent memory error, meaning it can no longer remember its settings or how to operate correctly.

High Engineer only £250-450

Parts commonly replaced

  • Main Printed Circuit Board (PCB)

Related codes

Showing 21–30 of 41
F.64

Your boiler's computer is struggling to read internal signals correctly and has stopped working to prevent potential damage.

High Engineer only £200-450

Parts commonly replaced

  • Main PCB
  • Wiring harness

Related codes

F.65

Your boiler's internal computer is overheating, causing the system to shut down to prevent damage to its sensitive electronic parts.

High Engineer only £150-300

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Wiring harness
  • Internal fan

Related codes

F.67

Your boiler is unable to safely detect if a flame is present, so it has purposefully shut itself down to prevent a gas safety risk.

High Engineer only £150-350

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Flame rectification electrode
  • Wiring harness

Related codes

F.68

Your boiler is struggling to keep the internal flame steady, so it has shut itself down to prevent any unsafe operation.

High Engineer only £180-350

Parts commonly replaced

  • Flame rectification electrode
  • Gas valve
  • Main printed circuit board (PCB)

Related codes

F.70

Your boiler's computer has lost its identity settings and no longer recognizes its own configuration, preventing it from functioning correctly.

High Engineer only £120-250

Parts commonly replaced

  • User Interface PCB
  • Main Control Board

Related codes

F.71

Your boiler is struggling to accurately measure the temperature of the water flowing through it, so it has stopped operating to prevent potential damage.

High Engineer only £150-250

Parts commonly replaced

  • Flow temperature sensor
  • Return temperature sensor
  • Wiring harness

Related codes

F.72

Your boiler is having trouble accurately reading the water levels or temperature inside the system, which is preventing it from heating your home safely.

High Engineer only £150-250

Parts commonly replaced

  • Water pressure sensor
  • NTC return temperature sensor
  • Wiring harness

Related codes

F.73

Your boiler's internal water pressure gauge is failing to signal correctly, which is preventing the system from running safely.

High Engineer only £150-250

Parts commonly replaced

  • Pressure sensor
  • Wiring harness

Related codes

F.74

Your boiler is having trouble reading its internal water pressure, which prevents it from safely igniting.

High Engineer only £150-250

Parts commonly replaced

  • Water pressure sensor
  • Wiring harness

Related codes

F.75

Your boiler is struggling to detect the water pressure inside the system because the sensor is failing to provide a clear reading.

High Engineer only £150-250

Parts commonly replaced

  • Water pressure sensor
  • Pressure expansion vessel

Related codes

Showing 31–40 of 41
F.76

Your boiler has detected a failure in a vital safety sensor that protects the heat exchanger from overheating, so it has shut itself down to prevent damage.

High Engineer only £180-350

Parts commonly replaced

  • Primary heat exchanger thermal fuse
  • Wiring harness
  • Main PCB

Related codes

F.77

Your boiler is struggling to clear water or exhaust gases, likely due to a blockage in the drainage pipe or a flue issue.

Emergency Engineer only £120-250

Parts commonly replaced

  • Condensate pump
  • Condensate trap
  • Flue seal
  • PCB

Related codes

F.78

Your boiler has lost the connection to the sensor that monitors your hot water temperature.

Medium Engineer only £120-220

Parts commonly replaced

  • DHW NTC sensor
  • Wiring harness
  • PCB

Related codes

F.83

Your boiler has detected that the water temperature readings are inconsistent or not changing as expected when the burner is lit, so it has shut down to prevent damage.

High Engineer only £150-250

Parts commonly replaced

  • NTC Temperature Sensor
  • Wiring harness

Related codes

F.84

Your boiler is having trouble measuring water temperatures accurately because it is receiving conflicting data from its internal sensors.

High Engineer only £150-250

Parts commonly replaced

  • Flow/return NTC thermistor sensor
  • Wiring harness

Related codes

F.85

Your boiler's internal temperature sensors are giving conflicting information, causing the system to stop working as a precaution.

High Engineer only £120-220

Parts commonly replaced

  • NTC Temperature Sensor
  • Wiring harness

Related codes

F.86

Your boiler has detected an issue with the link to your underfloor heating system, causing the unit to stop operating correctly.

High Engineer only £120-250

Parts commonly replaced

  • Underfloor heating contact sensor
  • Main PCB
  • Wiring harness

Related codes

F.87

Your boiler is failing to ignite because it cannot detect the spark needed to light the flame.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Ignition lead
  • Printed Circuit Board (PCB)

Related codes

F.88

Your boiler is unable to control the gas supply it needs to ignite, which means your heating and hot water have stopped working.

High Engineer only £180-350

Parts commonly replaced

  • Gas valve
  • Main PCB
  • Wiring harness

Related codes

F.89

Your boiler's water circulation pump is failing to start or is not responding as expected, which means the system cannot push hot water to your radiators or taps.

High Engineer only £200-350

Parts commonly replaced

  • Circulation Pump
  • Pump Wiring Harness
  • Main PCB

Related codes

Showing 41–41 of 41
F.91

Your boiler has lost the connection to the temperature sensor in your hot water cylinder, which means it cannot accurately monitor your hot water levels.

Medium Engineer only £120-220

Parts commonly replaced

  • Cylinder temperature sensor
  • Wiring harness

Related codes

53 operating states & engineer diagnostics

Not faults — these are normal operating states. Tap to expand.

P.01 Diagnostic Your boiler is currently running through a normal 15-minute start-up phase to reach its target heating level and is functioning exactly as it should. P.02 Diagnostic Your boiler is currently performing a routine start-up sequence and is running at a lower power level to safely ignite, which will automatically return to normal operation after 15 minutes. P.03 Diagnostic Your boiler is currently running at its maximum power setting to heat your home, which is a normal operational state rather than a fault. P.04 Diagnostic Your boiler is currently performing a temporary automatic test to ensure it is heating your water and radiators at the correct power levels. P.05 Diagnostic Your boiler is currently running an automatic filling or air-removal cycle and will resume normal operation once this 15-minute process completes. P.06 Diagnostic Your boiler is currently running an automated air-removal program to clear trapped bubbles from the system, which is a normal maintenance process. P.07 Diagnostic Your boiler is currently running an automated air-clearing cycle to remove trapped bubbles from its internal pipework. P.10 Diagnostic Your boiler has detected a safety concern and has temporarily shut itself down to prevent any damage or danger. S.0 Status Your boiler is perfectly healthy and is simply waiting for a signal from your thermostat to start heating your home or water. S.01 Status Your boiler is simply performing a routine safety check by clearing out the air inside before it ignites the flame. S.02 Status Your boiler is simply preparing to start the heating process by circulating water, and this is a normal part of its routine operation. S.03 Status Your boiler is currently in the process of attempting to light the flame to heat your home. S.04 Status Your boiler is operating normally and is currently firing up to provide heat to your radiators. S.05 Status Your boiler is currently cooling itself down after use and is operating exactly as it should. S.06 Status Your boiler is currently cooling itself down after being in use, which is a normal part of its shutdown process. S.07 Status Your boiler is currently running its pump to circulate leftover heat around your radiators, which is a normal part of the shutdown process. S.08 Status Your boiler is currently taking a short, scheduled break to manage its internal temperature before restarting the heating process. S.10 Status Your boiler is simply letting you know that it is currently preparing to provide you with hot water. S.11 Status Your boiler is simply performing a routine internal check of its fan system before starting the heating or hot water process. S.13 Status Your boiler is currently in the process of lighting the flame to heat your water, which is a standard part of its normal operation. S.14 Status Your boiler is currently operating normally as it heats water for your taps or shower. S.15 Status Your boiler is currently clearing out leftover heat after you have finished using the hot water, which is a normal part of the shutdown process. S.16 Status Your boiler is currently cooling itself down by running its internal fan after you have finished using the hot water taps. S.17 Status Your boiler is currently performing a standard safety procedure to move leftover hot water away from the heat exchanger after you have finished using the tap or shower. S.20 Status Your boiler is simply letting you know that it is currently busy heating up water for your taps or shower. S.21 Status Your boiler is currently just warming up its internal fan as part of its normal preparation process to provide you with hot water. S.22 Status Your boiler is simply preparing its internal pump to circulate water before it switches on to heat your hot water. S.23 Status Your boiler is currently in the process of starting up to heat your hot water and is operating normally. S.24 Status Your boiler is currently heating your hot water and is working exactly as it should. S.25 Status Your boiler is currently just finishing its cooling cycle after providing hot water and is not actually reporting a fault. S.26 Status Your boiler is currently cooling itself down after you finished using your hot water tap. S.27 Status Your boiler is currently performing a normal process where the internal pump runs for a short period after hot water usage to move residual heat away from the heat exchanger. S.28 Status Your boiler has temporarily turned off its heating flame because it has reached its intended temperature and is currently resting. S.30 Status Your boiler is working correctly, but it has been told by your wall-mounted thermostat to stay off, so it is waiting for a signal to start heating. S.31 Status Your boiler is currently in standby mode because it has not been asked to provide any heating or hot water, and it is functioning exactly as it should. S.32 Status Your boiler is struggling to get the internal fan spinning at the correct speed to safely vent gases, so it has paused operation to prevent any risk. S.33 Status Your boiler is pausing its startup sequence because it has detected an issue with the airflow system that needs to be cleared before it can safely ignite. S.34 Status Your boiler is temporarily protecting itself from freezing by running the pump, which is a normal feature during very cold weather. S.39 Status Your boiler has detected that the external safety switch for your underfloor heating system is currently turned off or disconnected, so it has paused heating to that area to prevent damage. S.41 Status Your boiler's internal water pressure is currently too high, which may cause it to stop working to protect the system from potential leaks or damage. S.42 Status Your boiler has detected that the flap which controls the airflow in your exhaust pipe is stuck shut, preventing it from venting waste gases properly. S.46 Status Your boiler has detected very cold weather and is briefly running its internal heating system to prevent the internal pipes from freezing. S.53 Status Your boiler is temporarily pausing its operation because it has detected that the water circulation inside your heating system is not flowing as efficiently as it should be. S.54 Status Your boiler is temporarily pausing because it has detected that the water pressure inside your heating system is too low for it to operate safely. S.76 Diagnostic Your boiler is simply reminding you that the water pressure inside your heating system has dropped and needs topping up. S.88 Status Your boiler is currently performing a routine automated process to clear trapped air from its internal system, so there is no need for alarm. S.91 Status Your boiler has been accidentally set to a demonstration mode used in showrooms, meaning it is not actually firing up to heat your home or water. S.96 Status Your boiler is currently performing an internal health check and has paused its heating functions while it verifies that its temperature sensors are working correctly. S.97 Status Your boiler is currently running a self-check to ensure its internal pressure sensors are working correctly, so it has temporarily paused your heating and hot water. S.98 Status Your boiler is currently running a self-diagnostic check, which is temporarily pausing your heating and hot water to ensure everything is operating safely. S.99 Status Your boiler is currently running an internal self-check to ensure all systems are functioning correctly before it starts heating your home. S.108 Status Your boiler is currently running a routine safety check to clear air out of the internal system before it begins a normal heating cycle. S.109 Status Your boiler is currently in a temporary power-saving standby state and is not actively heating your home or water.