Glow-worm Micron 30ff Fault codes & diagnostics

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

Regular Natural Gas 8.8 kW 1999-2002 Discontinued
GC Numbers 41-047-1641-047-46

Replaced by: Flexicom hx

Download the Glow-worm Micron 30ff 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.
7 High
Versions & GC numbers

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
41-047-16 Micron 30FF 1999–2002
41-047-46 Micron 30 FF 2001–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 Micron 30ff faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 7 documented codes

Tap any card for details

Illuminated reset light

Your boiler has switched itself off because it has reached an unsafe temperature and needs to be cooled down and reset.

High DIY-safe £100-280

What to check first

  1. Check that your radiator valves are open and not turned to zero.
  2. Turn the boiler temperature control knob to the 'O' position.
  3. Wait a few minutes for the unit to cool, then turn the knob back to your desired temperature setting to reset the fault.

Parts commonly replaced

  • Overheat Thermostat
  • Circulation Pump
  • Thermistor
Full explanation for Illuminated reset light
NEON5

Your boiler has shut down because it has detected it is getting too hot, usually caused by a blockage or a pump failure.

High DIY-safe £120-280

What to check first

  1. Check that your pump is running and hasn't seized
  2. Ensure all radiator valves are open to allow water to flow
  3. Wait for the boiler to cool down and press the reset button located underneath the unit

Parts commonly replaced

  • Circulating Pump
  • Overheat Thermostat
  • Thermistor

Related codes

Full explanation for NEON5
NEON6

Your boiler is failing to light or stay lit, meaning it cannot heat your home or water.

High DIY-safe £120-350

What to check first

  1. Check if your gas supply is active, for example by testing another gas appliance like a hob.
  2. Press the reset button once to see if the boiler restarts.
  3. Ensure the condensate pipe (the white plastic pipe outside) hasn't frozen in cold weather.

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • Printed Circuit Board (PCB)

Related codes

Full explanation for NEON6
Reset LED is lit

Your boiler has sensed it is getting too hot and has shut itself down as a safety precaution.

High DIY-safe £100-280

What to check first

  1. Check that all radiator valves are open and not turned to zero.
  2. Ensure there are no blockages in the system and that the pump is running.
  3. Reset the boiler by turning the temperature control knob to 'Off' and then back to your desired setting.

Parts commonly replaced

  • Overheat Thermostat
  • Circulation Pump
  • Temperature Sensor (NTC Thermistor)
Full explanation for Reset LED is lit
Reset light

Your boiler has switched itself off because it got too hot, likely triggered by a safety sensor to prevent damage.

High DIY-safe £120-250

What to check first

  1. Open the small control cover on the front of the boiler.
  2. Turn the temperature control knob fully anticlockwise to the '0' position.
  3. Wait a few seconds, then turn the knob back to your original desired temperature setting to restart the boiler.

Parts commonly replaced

  • Overheat Thermostat
  • Circulation Pump
  • Thermistor
Full explanation for Reset light
Reset Light / Overheat

Your boiler has switched itself off because it has reached an unsafe temperature, usually caused by a circulation issue or a temporary blockage.

High DIY-safe £0-180

What to check first

  1. Open the control cover on the front of the boiler
  2. Turn the temperature control knob fully anticlockwise to the '0' position
  3. Wait a few seconds, then turn the knob back to your original desired temperature setting to restart the boiler

Parts commonly replaced

  • Overheat Thermostat
  • Pump
  • Thermistor
Full explanation for Reset Light / Overheat
Software Error

Your boiler's internal computer brain has encountered a glitch or failure and is struggling to run its operating system.

High DIY-safe £280-450

What to check first

  1. Switch the boiler's electrical power supply off at the fused spur switch
  2. Wait for approximately 60 seconds
  3. Switch the power back on and see if the error clears

Parts commonly replaced

  • Main Printed Circuit Board (PCB)
Full explanation for Software Error
Status & diagnostic codes

7 operating states & engineer diagnostics

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

Burner On neon off Status Your boiler's burner stays lit even when it should turn off, meaning it isn't responding to your thermostat or timer settings. F4A Diagnostic Your boiler has stopped working because an internal electrical safety fuse has blown, meaning the system is currently unable to power itself safely. NEON1 Status Your boiler is receiving electrical power and is in standby mode or waiting for a signal to heat up. NEON2 Status Your boiler is receiving a request to turn on the heating or hot water, but it has not yet successfully fired the burner. NEON3 Status Your boiler has stopped working because it thinks the fan is spinning but it isn't receiving the correct signal to proceed with lighting the burner. NEON4 Status Your boiler is operating normally and the burner has successfully ignited to provide heating or hot water. T3.15A Diagnostic Your boiler has stopped working because an internal safety fuse has blown, likely due to an electrical fault or power surge.