Glow-worm Flexicom hxi Fault codes & diagnostics

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

Regular Natural Gas 12-38 kW 2006 onwards Discontinued

Replaced by: Easicom

Download the Glow-worm Flexicom hxi 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.
8 High

All 8 documented codes

Tap any card for details

F4

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

High Engineer only £120-220

Parts commonly replaced

  • Return thermistor sensor
  • Wiring harness

Related codes

F6

Your boiler's main control panel is having trouble communicating with the internal computer system, preventing the unit from starting safely.

High Engineer only £150-300

Parts commonly replaced

  • UI interface harness
  • Main printed circuit board (PCB)

Related codes

F10

Your boiler has detected that the electricity supply reaching it is too low to operate safely, causing it to shut down to prevent damage.

High Engineer only £120-250

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Power supply wiring/fused spur

Related codes

F13

Your boiler is struggling to get rid of the wastewater it produces, causing it to block its exhaust system as a safety precaution.

High Engineer only £120-250

Parts commonly replaced

  • Condensate siphon
  • Air pressure switch
  • Condensate trap

Related codes

F22

Your boiler has stopped because the water pressure inside the heating system has dropped too low to operate safely.

High DIY-safe £80-150

What to check first

  1. Locate the external filling loop, which is a flexible silver hose connected to the pipework underneath the boiler.
  2. Open the two valves at either end of the filling loop to allow water into the system, watching the pressure gauge on the front of the boiler.
  3. Once the needle reaches the green zone (typically between 1.0 and 1.5 bar), tightly close both valves and ensure no water is leaking from the loop.

Parts commonly replaced

  • Pressure relief valve
  • Pressure sensor
  • Expansion vessel
F25

Your boiler has detected that water is not circulating through your heating system correctly, causing it to overheat and shut down for safety.

High Engineer only £150-350

Parts commonly replaced

  • Central Heating Pump
  • System Filter
  • Diverter Valve

Related codes

F43

Your boiler has detected a communication issue between its internal parts, meaning it has safely shut itself down to prevent potential damage.

High Engineer only £150-300

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Wiring harness

Related codes

F70

Your boiler's internal computer is experiencing a communication error, meaning it has lost track of its own settings and cannot function safely.

High Engineer only £150-300

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • User Interface Module

Related codes