Glow-worm Energy7 25s-A Fault codes & diagnostics

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

System Natural Gas
GC Number 41-019-56
Download the Glow-worm Energy7 25s-A manualThe official installation and service manual (PDF), the document these fault codes were read from. 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.
4 Emergency 31 High 6 Medium

All 41 documented codes

Tap any card for details

F.00

Your boiler has temporarily stopped working because it has lost the signal from one of its internal temperature sensors.

High Engineer only £90-180

Parts commonly replaced

  • Flow temperature sensor (NTC)
  • Wiring harness

Related codes

F.01

Your boiler has temporarily stopped working because it cannot properly read the temperature of the water returning to it.

High Engineer only £90-180

Parts commonly replaced

  • Return temperature sensor
  • Wiring harness

Related codes

F.10

Your boiler has stopped working because it cannot properly read the water temperature due to a faulty sensor or wiring issue.

High Engineer only £120-250

Parts commonly replaced

  • Flow temperature sensor
  • Wiring harness

Related codes

F.11

Your boiler has detected a faulty reading from an internal water temperature sensor, which temporarily stops the heating system from operating safely.

High Engineer only £120-£200

Parts commonly replaced

  • Return NTC temperature sensor
  • Wiring harness

Related codes

F.12

Your boiler has detected a faulty signal from the hot water cylinder sensor, meaning it cannot properly monitor your stored hot water temperature.

Medium Engineer only £90-180

Parts commonly replaced

  • Cylinder temperature sensor
  • Wiring harness

Related codes

F.13

Your boiler is receiving a confused signal from the sensor that monitors your hot water tank temperature, likely due to a loose wire or a faulty sensor connection.

Medium Engineer only £120-220

Parts commonly replaced

  • Cylinder NTC sensor
  • Wiring harness

Related codes

F.20

Your boiler has detected that it is running too hot and has automatically turned itself off as a safety precaution to prevent damage.

High Engineer only £120-250

Parts commonly replaced

  • NTC sensor
  • Ignition lead
  • Wiring harness

Related codes

F.22

Your boiler has stopped working because it has detected that the water pressure inside the system is too low to run safely.

High DIY-safe £100-250

What to check first

  1. Locate the external filling loop, which is a silver braided hose connecting your central heating pipework to the mains water supply.
  2. Gradually open the valves on the filling loop to allow water into the system until the boiler's pressure gauge reads between 1.0 and 1.5 bar.
  3. Once the pressure is correct, ensure both valves on the filling loop are turned fully off and the system resets itself.

Parts commonly replaced

  • Water pressure sensor
  • Pressure relief valve
  • Expansion vessel

Related codes

F.23

Your boiler has detected that water is failing to circulate correctly through the heating system, causing a rapid and unsafe temperature difference inside the unit.

High Engineer only £150-350

Parts commonly replaced

  • Central heating pump
  • NTC sensor
  • Printed Circuit Board

Related codes

F.24

Your boiler has shut down because the internal water temperature is rising much too quickly, which usually points to a blockage, trapped air, or a problem with water circulation.

High DIY-safe £150-350

What to check first

  1. Check your boiler pressure gauge to ensure it is sitting between 1 and 1.5 bar, and top it up using the filling loop if it is too low.
  2. Bleed your radiators starting from the ground floor up to remove any trapped air from the system.
  3. Check that your thermostatic radiator valves and any external zone valves are fully open.

Parts commonly replaced

  • Central heating pump
  • Automatic air vent
  • Heat exchanger

Related codes

Showing 11–20 of 41
F.25

Your boiler has detected that the flue gases are getting too hot or that a safety connection inside the unit has come loose, causing it to shut down to prevent damage.

High Engineer only £120-250

Parts commonly replaced

  • Flue gas safety cut-out sensor
  • Wiring harness
  • PCB

Related codes

F.27

Your boiler has detected a problem with its internal flame-sensing system and has shut itself down as a safety precaution.

Emergency Engineer only £150-350

Parts commonly replaced

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

Related codes

F.28

Your boiler is failing to light the flame needed to produce heat and hot water, which typically indicates a problem with the gas supply or the ignition components.

High Engineer only £150-350

Parts commonly replaced

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

Related codes

F.29

Your boiler has stopped working because it cannot keep its internal flame lit, which means it is unable to produce heat or hot water.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Ignition lead

Related codes

F.32

Your boiler has detected that the internal fan responsible for moving air is not spinning at the correct speed or is being held back by a loose connection.

High Engineer only £180-350

Parts commonly replaced

  • Fan assembly
  • Wiring harness
  • Main PCB

Related codes

F.49

Your boiler's communication system is experiencing an electrical issue, which is likely preventing it from receiving the signal to turn on your heating or hot water.

High Engineer only £120-250

Parts commonly replaced

  • eBUS wiring harness
  • PCB (Printed Circuit Board)
  • External heating controls

Related codes

F.61

Your boiler has detected an electrical fault within the internal component that controls the gas supply, meaning it has safely shut itself down to prevent any risk.

High Engineer only £180-350

Parts commonly replaced

  • Gas valve assembly
  • Wiring harness
  • Main PCB

Related codes

F.62

Your boiler has detected that the gas inside is not switching off correctly when it should, which is a safety concern that prevents the system from operating.

Emergency Engineer only £250-450

Parts commonly replaced

  • Gas valve
  • Main PCB

Related codes

F.63

Your boiler's internal computer is experiencing a memory error, meaning it has lost its settings and cannot safely manage the heating process.

High Engineer only £250-450

Parts commonly replaced

  • Main PCB (Printed Circuit Board)

Related codes

F.64

Your boiler has detected a faulty signal from its internal sensors, which means it cannot accurately measure the temperature of the water flowing through it and has safely shut down to prevent damage.

High Engineer only £150-250

Parts commonly replaced

  • NTC Temperature Sensor
  • Main Printed Circuit Board (PCB)

Related codes

Showing 21–30 of 41
F.65

Your boiler's computer system is getting too hot and has automatically shut down to prevent permanent damage.

High Engineer only £150-350

Parts commonly replaced

  • Main printed circuit board (PCB)
  • Control unit

Related codes

F.67

Your boiler has detected an internal error with its computer chip that processes the flame safety signal, which means it has safely shut down to prevent unsafe operation.

High Engineer only £250-450

Parts commonly replaced

  • Main PCB (Printed Circuit Board)

Related codes

F.68

Your boiler is struggling to keep the flame lit reliably because it is having trouble accessing or processing its fuel supply properly.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Wiring harness

Related codes

F.70

Your boiler has lost its identity settings, usually because a part was recently replaced and not correctly programmed to match your specific model.

High Engineer only £100-200

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Coding resistor

Related codes

F.71

Your boiler is confused because it is getting incorrect information about how hot the water is inside the system, so it has stopped working as a safety precaution.

High Engineer only £150-250

Parts commonly replaced

  • Flow temperature sensor (NTC)
  • Wiring harness

Related codes

F.72

Your boiler has detected that the water temperature is behaving unexpectedly, suggesting that its internal heat sensors are likely providing conflicting or inaccurate information.

High Engineer only £150-250

Parts commonly replaced

  • NTC Temperature Sensor
  • Pressure Sensor

Related codes

F.73

Your boiler's internal sensor that measures water pressure is malfunctioning or disconnected, preventing the system from knowing if it is safe to fire up.

High Engineer only £150-250

Parts commonly replaced

  • Water pressure sensor
  • Wiring harness

Related codes

F.74

Your boiler has detected an electrical fault with its internal water pressure sensor.

Medium Engineer only £120-200

Parts commonly replaced

  • Water pressure sensor
  • Wiring harness

Related codes

F.75

Your boiler has noticed that the water pressure sensor is not detecting the expected pressure spike when the pump starts up.

High Engineer only £120-250

Parts commonly replaced

  • Water pressure sensor
  • Pressure switch

Related codes

F.76

Your boiler has detected a safety disagreement between its internal temperature protection device and the gas control system, so it has safely shut down to prevent any risk.

Emergency Engineer only £150-350

Parts commonly replaced

  • Primary heat exchanger safety thermal fuse
  • Gas valve assembly
  • Main printed circuit board (PCB)

Related codes

Showing 31–40 of 41
F.77

Your boiler has detected an issue with the drainage of exhaust gases or water, meaning it has shut down to prevent the release of harmful fumes into your home.

Emergency Engineer only £150-300

Parts commonly replaced

  • Flue non-return flap
  • Condensate trap
  • PCB

Related codes

F.78

Your boiler has lost its hot water temperature reading because an optional external control or link connection is not set up correctly.

Medium Engineer only £90-180

Parts commonly replaced

  • Domestic Hot Water NTC Sensor
  • Link Box / Wiring Harness

Related codes

F.83

Your boiler is failing to detect a rise in water temperature when the flame ignites, which usually means there is air trapped inside or not enough water circulating through the system.

High Engineer only £120-250

Parts commonly replaced

  • NTC Temperature Sensor
  • Central Heating Pump

Related codes

F.84

Your boiler has detected a mix-up or incorrect reading between its internal temperature sensors, which usually means they were installed backwards or have come loose during maintenance.

High Engineer only £90-180

Parts commonly replaced

  • Flow temperature sensor
  • Return temperature sensor
  • Wiring harness

Related codes

F.85

Your boiler has detected that its internal temperature sensors are either disconnected or have been accidentally moved to the wrong pipes during installation or maintenance work.

High Engineer only £120-250

Parts commonly replaced

  • NTC Temperature sensors
  • Wiring harness

Related codes

F.86

Your boiler has detected that the connection to your underfloor heating system is interrupted or a safety sensor is not reporting correctly, so it has stopped providing heat to prevent damage.

Medium Engineer only £120-250

Parts commonly replaced

  • Underfloor heating contact sensor
  • Wiring harness
  • Main PCB

Related codes

F.87

Your boiler is failing to detect the internal spark needed to ignite the flame, meaning it cannot start up to provide heat or hot water.

High Engineer only £120-250

Parts commonly replaced

  • Ignition lead
  • Ignition electrode
  • Wiring harness

Related codes

F.88

Your boiler has lost its connection to the component that controls the gas supply, meaning it cannot safely ignite to provide heating or hot water.

High Engineer only £150-300

Parts commonly replaced

  • Gas valve
  • Wiring harness

Related codes

F.89

Your boiler has detected that the internal pump, which moves water around your heating system, is not communicating correctly with the main control board.

High Engineer only £180-350

Parts commonly replaced

  • Circulation pump
  • Wiring harness
  • Main printed circuit board (PCB)

Related codes

F.91

Your boiler has detected a faulty reading from the sensor that measures the temperature of your hot water cylinder, usually due to a wiring issue or a broken sensor.

Medium Engineer only £90-180

Parts commonly replaced

  • Cylinder temperature sensor
  • Wiring harness

Related codes

Showing 41–41 of 41
F.97

Your boiler's internal computer has failed its own safety check and can no longer control the heating system, meaning the unit will not operate.

High Engineer only £250-450

Parts commonly replaced

  • Main Printed Circuit Board (PCB)

Related codes

Avoid the next call-out bill

Monthly cover means no unexpected bills when your boiler breaks down.

Approved partner
Domestic Appliance Guard
Unlimited call-outs, 24/7 helpline, no price-hike promise
Get a quote →

Affiliate links. We may earn a commission at no extra cost to you.