Glow-worm Easicom3 Combi Fault codes & diagnostics

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

Combi Natural Gas 24-28 kW 2017 onwards
GC Numbers 47-019-5047-019-51
Download the Glow-worm Easicom3 Combi manual The official installation & service manual (PDF) — the exact document these fault codes were verified against. PDF

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.
1 Emergency 36 High 2 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
47-019-50 EASICOM 3 24c-A (H-GB) 2017–present
47-019-51 EASICOM 3 28c-A (H-GB) 2017–present

All 39 documented codes

Tap any card for details

F.00

Your boiler is unable to measure the temperature of the water inside it, so it has safely shut down to prevent overheating.

High Engineer only £120-180

Parts commonly replaced

  • NTC Temperature Sensor
  • Wiring harness

Related codes

F.01

Your boiler is struggling to accurately measure the temperature of the water returning to it, so it has stopped working to prevent potential overheating.

High Engineer only £150-250

Parts commonly replaced

  • Return temperature sensor
  • Wiring harness

Related codes

F.10

Your boiler has stopped working because it is unable to accurately measure the temperature of the water inside it, likely due to a faulty sensor or damaged wiring.

High Engineer only £120-220

Parts commonly replaced

  • Flow temperature sensor (NTC)
  • Wiring harness

Related codes

F.11

Your boiler has detected a faulty signal from its internal temperature sensor, causing it to shut down for safety to prevent overheating.

High Engineer only £120-220

Parts commonly replaced

  • Return temperature sensor
  • Wiring harness

Related codes

F.13

Your boiler is having trouble reading the temperature of your hot water supply because a sensor connection is faulty.

High Engineer only £120-220

Parts commonly replaced

  • NTC Temperature Sensor
  • Wiring Harness

Related codes

F.20

Your boiler has detected that it is running too hot and has automatically switched itself off to prevent damage to its internal parts.

High Engineer only £120-250

Parts commonly replaced

  • NTC Sensor
  • Pump
  • Heat Exchanger

Related codes

F.22

Your boiler has stopped working because the water pressure inside the heating system has dropped too low.

High DIY-safe £80-150

What to check first

  1. Locate the filling loop under the boiler, which usually consists of one or two flexible braided hoses with small levers or valves.
  2. Open the valves slowly to allow mains water to enter the system until the pressure gauge on the front of the boiler reads between 1.0 and 1.5 bar.
  3. Close the valves tightly and check the boiler display to see if the error code has cleared.

Parts commonly replaced

  • Pressure relief valve
  • Expansion vessel
  • Pressure sensor

Related codes

F.23

Your boiler has detected that the water is not flowing correctly through the system, causing a temperature difference that has triggered a safety shutdown to prevent damage.

High Engineer only £150-300

Parts commonly replaced

  • Central heating pump
  • Flow sensor
  • NTC thermistor sensors

Related codes

F.24

Your boiler is shutting down because the water inside is heating up much faster than it is moving through the system.

High Engineer only £150-300

Parts commonly replaced

  • Central heating pump
  • System filter
  • Heat exchanger

Related codes

F.25

Your boiler has detected that the exhaust gases are getting too hot and has automatically shut down to prevent damage to its internal components.

High Engineer only £150-300

Parts commonly replaced

  • NTC Sensor
  • Heat exchanger
  • Pump

Related codes

Showing 11–20 of 39
F.27

Your boiler has detected an issue with the flame and has safely shut down to prevent gas from being released without burning.

High Engineer only £150-300

Parts commonly replaced

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

Related codes

F.28

Your boiler is trying to start up but is failing to light the gas flame, so it has shut down to keep your home safe.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Ignition lead

Related codes

F.29

Your boiler is struggling to stay lit because the gas supply is being interrupted or the flame is not being detected properly.

High Engineer only £150-300

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Flame rectification probe

Related codes

F.32

Your boiler has detected that the fan, which pushes waste gases outside, is running at the wrong speed and has paused for safety.

High Engineer only £150-300

Parts commonly replaced

  • Fan assembly
  • Printed Circuit Board (PCB)
  • Wiring harness

Related codes

F.49

Your boiler is having a communication problem with its smart controls, which is preventing it from receiving clear instructions on when to turn the heating or hot water on.

High Engineer only £120-250

Parts commonly replaced

  • eBUS communication cable
  • PCB (Printed Circuit Board)
  • External thermostat or smart controller

Related codes

F.61

Your boiler has detected an issue with the internal component that controls the flow of gas, meaning it cannot safely start up to provide heating or hot water.

High Engineer only £250-450

Parts commonly replaced

  • Gas valve assembly
  • Main PCB

Related codes

F.62

Your boiler has detected an issue with how the gas supply is being turned on or off, meaning it has safely shut itself down to prevent any unsafe conditions.

High Engineer only £150-300

Parts commonly replaced

  • Gas valve
  • Printed Circuit Board (PCB)

Related codes

F.63

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

High Engineer only £250-450

Parts commonly replaced

  • Main PCB

Related codes

F.64

Your boiler's computer is having trouble reading its internal sensors, which is causing it to shut down to prevent incorrect operation.

High Engineer only £200-400

Parts commonly replaced

  • Main printed circuit board (PCB)
  • Wiring harness

Related codes

F.65

Your boiler’s internal control board is getting too hot, so it has safely shut itself down to prevent any damage to its electronic components.

High Engineer only £150-350

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Wiring harness

Related codes

Showing 21–30 of 39
F.67

Your boiler's computer is struggling to identify the flame correctly, which has caused it to stop running to keep you safe.

High Engineer only £200-450

Parts commonly replaced

  • Main PCB
  • Flame rectification lead

Related codes

F.68

Your boiler is having trouble keeping a steady flame, causing it to shut down for safety reasons.

High Engineer only £150-350

Parts commonly replaced

  • Flame sensor electrode
  • Gas valve
  • Printed Circuit Board (PCB)

Related codes

F.70

Your boiler’s internal computer has forgotten its identity, meaning it does not know which model it is or how to operate correctly.

High Engineer only £150-250

Parts commonly replaced

  • User Interface PCB
  • Main PCB

Related codes

F.71

Your boiler has stopped working because it cannot correctly measure the temperature of the water flowing through the system.

High Engineer only £150-250

Parts commonly replaced

  • NTC sensor
  • Wiring harness

Related codes

F.72

Your boiler is having trouble comparing internal temperature and pressure readings, meaning it has safely shut down to prevent damage.

High Engineer only £150-250

Parts commonly replaced

  • NTC temperature sensor
  • Water pressure sensor
  • Printed Circuit Board

Related codes

F.73

Your boiler's sensor that monitors water pressure is not sending a proper signal, which prevents the boiler from starting safely.

High Engineer only £150-250

Parts commonly replaced

  • Water pressure sensor
  • Wiring harness

Related codes

F.74

Your boiler is struggling to accurately detect the water pressure, which prevents it from safely igniting to heat your home or water.

High Engineer only £150-250

Parts commonly replaced

  • Water pressure sensor
  • Wiring harness

Related codes

F.75

Your boiler is struggling to accurately detect the water pressure inside the system, which is preventing it from starting up reliably.

High Engineer only £150-250

Parts commonly replaced

  • Water pressure sensor
  • Pressure relief valve

Related codes

F.77

Your boiler has detected an issue with the system that drains wastewater away, which is preventing it from operating safely.

High Engineer only £120-250

Parts commonly replaced

  • Condensate pump
  • Condensate trap
  • External discharge pipework

Related codes

F.78

Your boiler has lost communication with an external hot water accessory, meaning it is unsure how to correctly provide your hot water.

Medium Engineer only £120-200

Parts commonly replaced

  • External DHW sensor
  • Wiring harness
  • Main PCB

Related codes

Showing 31–39 of 39
F.83

Your boiler has detected that there is not enough water circulating inside the system to operate safely, which prevents it from firing up.

High DIY-safe £80-150

What to check first

  1. Check your boiler's pressure gauge on the front display.
  2. If the needle is below 1 bar, locate the filling loop (usually a silver braided hose under the boiler).
  3. Open the valves on the filling loop to allow cold mains water into the system until the gauge reaches 1.5 bar, then close the valves tightly.

Parts commonly replaced

  • Flow sensor
  • Pressure sensor
  • Central heating pump

Related codes

F.84

Your boiler is confused because it is getting conflicting temperature readings, so it has shut down as a precaution to prevent overheating.

High Engineer only £120-220

Parts commonly replaced

  • NTC Sensor
  • Wiring harness

Related codes

F.85

Your boiler has detected that one of its temperature sensors is giving an incorrect or impossible reading, so it has shut down to prevent potential overheating.

High Engineer only £120-200

Parts commonly replaced

  • NTC temperature sensor
  • Wiring harness

Related codes

F.86

Your boiler has detected that the safety switch for your underfloor heating system is not sending the correct signal, which is preventing the heating from turning on.

Medium Engineer only £120-220

Parts commonly replaced

  • Underfloor heating interface module
  • Wiring harness
  • PCB

Related codes

F.87

Your boiler is failing to light the flame properly, which means it cannot produce hot water or heating for your home.

High Engineer only £150-250

Parts commonly replaced

  • Ignition electrode
  • Ignition lead
  • Ignition transformer

Related codes

F.88

Your boiler has detected a problem with the internal mechanism that controls the gas supply, meaning it cannot safely ignite to provide heating or hot water.

Emergency Engineer only £200-350

Parts commonly replaced

  • Gas valve assembly
  • Wiring harness
  • PCB

Related codes

F.89

Your boiler has detected that the internal mechanism responsible for moving water around your heating system is not working correctly.

High Engineer only £200-400

Parts commonly replaced

  • Circulation Pump
  • Pump Lead
  • Printed Circuit Board (PCB)

Related codes

F.97

Your boiler's internal computer is having trouble starting up correctly, which prevents it from operating safely.

High Engineer only £250-450

Parts commonly replaced

  • Main PCB

Related codes

F22

Your boiler has stopped working because the water pressure inside the heating system has dropped too low.

High DIY-safe £0-£120

What to check first

  1. Locate the filling loop (usually a silver braided hose with one or two valves) underneath your boiler.
  2. Open the valve(s) slowly to allow cold mains water into the system until the pressure gauge reads between 1.0 and 1.5 bar.
  3. Close the valve(s) tightly and your boiler should automatically restart.

Parts commonly replaced

  • Filling loop
  • Pressure relief valve
  • Expansion vessel

Related codes

51 operating states & engineer diagnostics

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

P.01 Diagnostic Your boiler is currently running a brief self-test to calibrate its heat output and will return to normal operation automatically shortly. P.02 Diagnostic Your boiler is currently running through a standard startup cycle and is operating at a controlled power level, which is a normal process that happens automatically after ignition. P.03 Diagnostic Your boiler is currently running at its maximum heating power because a manual setting has been adjusted in the service menu. P.04 Diagnostic Your boiler is currently running a manual testing mode intended for technicians, which forces it to operate at high heat for a short period. P.05 Diagnostic Your boiler has detected low water pressure and is automatically attempting to refill itself and clear any trapped air from the system. P.06 Diagnostic Your boiler is currently running an automated self-cleaning cycle to clear trapped air from the system pipes. P.07 Diagnostic Your boiler is currently running a brief, automatic self-cleaning process to remove trapped air from its internal pipes and will return to normal operation shortly. S.0 Status Your boiler is currently in standby mode because it has not been asked to provide any heating or hot water. S.01 Status Your boiler is currently preparing to ignite by running its internal fan, which is a normal part of the start-up sequence. S.02 Status Your boiler is simply preparing to heat your home by circulating water through the pipes before the burners ignite. S.03 Status Your boiler is currently trying to light the gas flame to start heating your home or water. S.04 Status Your boiler is operating normally and is currently firing up to heat your radiators or provide hot water. S.05 Status Your boiler is currently running a routine process to circulate or cool down water after the heating has turned off, and this code is simply a status message rather than a sign of a fault. S.06 Status Your boiler is currently running its internal fan to clear out lingering gases after the heating has switched off, which is a normal part of the shutdown process. S.07 Status Your boiler is simply finishing its normal cooling process by circulating water after the heating has switched off. S.08 Status Your boiler is currently taking a short, scheduled break after completing a heating cycle to allow its internal temperatures to stabilize. S.10 Status Your boiler is currently just letting you know it is preparing to heat your hot water, and this message should disappear as soon as the water starts warming up. S.11 Status Your boiler is currently preparing itself by clearing out its internal air chambers before igniting to heat your water. S.13 Status Your boiler is currently in the process of lighting the flame to provide you with hot water. 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 running its cooling cycle after you have finished using hot water or heating, which is a normal part of its operation. S.16 Status Your boiler is currently running its internal cooling fan to safely clear excess heat after you have finished using hot water. S.17 Status Your boiler is currently performing a standard internal cooling process after you finished using your hot water. S.20 Status Your boiler is currently operating normally as it prepares to heat your water. S.21 Status Your boiler is currently performing a standard internal safety check before firing up, which is a normal part of its operating cycle. S.22 Status Your boiler is simply performing a routine internal check and preparing the internal pump before it starts heating your water; this is a normal operating status and not a fault. S.23 Status Your boiler is currently performing a normal safety check as it prepares to light the burner to provide you with hot water. S.24 Status Your boiler is currently operating normally to provide hot water to your taps or shower. S.25 Status Your boiler is simply performing a routine cooling-down process after you have finished using hot water, and it will return to normal shortly. S.26 Status Your boiler is simply finishing a routine cleaning cycle to clear out leftover gases after you finished using your hot water. S.27 Status Your boiler is simply finishing a routine cooling process after providing hot water and should return to normal operation shortly. S.28 Status Your boiler is momentarily pausing its burner to regulate the water temperature, which is a normal part of its internal operation. S.30 Status Your boiler is currently prevented from turning on the heating because it is waiting for a signal from your wall thermostat or room controller. S.31 Status Your boiler is perfectly healthy and is simply waiting for a signal because it has been set to summer mode or the room thermostat is currently satisfied. S.32 Status Your boiler's air extraction system is not running at the correct speed, preventing the unit from safely igniting. S.33 Status Your boiler is temporarily running its internal fan to safely clear out any gases before it attempts to start up again. S.34 Status Your boiler has detected very cold temperatures and is briefly running its pump to prevent the internal pipes from freezing. S.39 Status Your boiler is signalling that it cannot detect an active connection to your underfloor heating system, meaning that part of your home heating may not be working. S.41 Status Your boiler has detected that the water pressure inside the heating system has risen above the safe limit. S.42 Status Your boiler has detected that a safety flap in the exhaust flue is stuck, preventing the appliance from starting safely. S.46 Status Your boiler has temporarily paused to prevent overheating because the water flow through the system is too low. S.53 Status Your boiler has temporarily stopped because the water pressure inside the system is too low, or the water is not circulating between the boiler and your radiators properly. S.54 Status Your boiler has detected that the water pressure inside your heating system is too low to operate safely, so it has temporarily paused to prevent damage. S.88 Status Your boiler is currently running an automatic process to clear trapped air from its internal system, which is a normal part of its maintenance routine. S.91 Status Your boiler has been accidentally set to a 'showroom' display mode which prevents it from heating your home or water. S.96 Status Your boiler is currently running a self-diagnostic test or internal check, which is temporarily preventing it from firing up for heating or hot water. S.97 Status Your boiler is currently running a self-diagnostic check, which is temporarily preventing it from heating your home or water. S.98 Status Your boiler is currently running a self-diagnostic test or has encountered a communication error with its internal temperature monitoring system, which has temporarily disabled your heating and hot water. S.99 Status Your boiler is currently refilling its internal water level automatically and will resume normal operation once the process is complete. S.108 Status Your boiler is currently running a brief automatic safety check to clear out any leftover gases before starting up. S.109 Status Your boiler has entered a temporary sleep mode and is currently not heating your water or home.

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