BoilerFaultCodes.com

Glow-worm Ultimate 100ff 120ff Fault Codes

Regular Natural Gas 30-38 kW 1994-2004 Discontinued
GC Numbers: 41-313-5441-313-55

Replaced by: Flexicom hx

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Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →

Most common fault codes

F1
Your boiler has lost power to its internal electronics, likely caused by a safety fuse blowing or an electrical fault inside the unit.
Gas Safe engineer required · £90-220
F2
Your boiler has likely experienced an internal electrical fault or a component failure that has caused a safety fuse on the main control board to blow.
Gas Safe engineer required · £120-280
Fan does not run
Your boiler has stopped working because the internal fan, which safely exhausts fumes, isn't starting up.
Gas Safe engineer required · £250-£480

All 18 fault codes

Code Severity Plain English
F1 High Your boiler has lost power to its internal electronics, likely caused by a safety fuse blowing or an electrical fault inside the unit.
F2 High Your boiler has likely experienced an internal electrical fault or a component failure that has caused a safety fuse on the main control board to blow.
Fan does not run High Your boiler has stopped working because the internal fan, which safely exhausts fumes, isn't starting up.
Fan hunts High Your boiler is struggling to maintain a steady fan speed, which is preventing it from completing its startup sequence and heating your home.
Main burner does not light High Your boiler is failing to ignite the main gas burner, which means you will have no heating or hot water until it is repaired.
Neon 1 lit High Your boiler has detected an electrical supply issue, likely caused by a tripped switch, a blown fuse, or a temporary power failure.
neon 1 not lit High Your boiler is not receiving electrical power or has an internal blown fuse, meaning it cannot start the ignition process.
Neon 2 lit High Your boiler has detected that the water pressure is too low to operate safely, causing it to lock out.
neon 2 not lit High Your boiler has switched itself off because it has reached an unsafe temperature or it has detected a faulty component in its safety system.
Neon 3 lit High Your boiler has detected an internal electrical communication fault which is preventing it from starting up safely.
neon 3 not lit High Your boiler is unable to safely clear exhaust fumes, which prevents it from firing up to provide heat or hot water.
Neon 4 lit High Your boiler is failing to light the small internal flame needed to start the main burner, which means your heating and hot water will not work.
neon 4 not lit High Your boiler is failing to light the gas or cannot confirm that a flame is present, meaning the system has shut down for safety.
Neon1 High Your boiler has lost power because of an electrical issue or a blown fuse inside the control unit.
Neon2 High Your boiler has switched itself off because it has either become too hot or the water pressure in the system has dropped too low.
Neon3 High Your boiler has stopped working because it cannot safely confirm that the fan is clearing exhaust gases from the system.
Neon4 High Your boiler is attempting to start but cannot successfully light or detect a steady flame, so it has shut down for safety.
Pilot does not light High Your boiler is failing to start up because the small ignition flame is not lighting correctly.

Glow-worm Ultimate 100ff 120ff is discontinued — time for a new one?

Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.

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