Common problems guide

The most common Glow-worm Betacom4 problems

The faults most likely to send a Glow-worm Betacom4 into lockout — with plain-English causes, what to check first, estimated repair costs and whether you need a Gas Safe engineer.

38 documented codes
6 most common
2 DIY-safe checks
4 engineer needed

The 6 most common faults

01
F22 High DIY-safe

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

What to try first

Locate the two small filling loop taps or the external filling key under the boilerSlowly open the tap or turn the key to allow water into the systemMonitor the pressure gauge on the front panel until the needle reaches the green zone (typically between 1.0 and 1.5 bar)Close the tap or key tightly and ensure no water is leaking from the connection

Est. cost
£80-150
Parts
Filling loop, Pressure relief valve, Expansion vessel
Full guide for F22
02
F.22 High DIY-safe

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

What to try first

Locate the filling loop (a silver flexi-hose) underneath the boilerOpen the valves on the filling loop to allow cold mains water to enter the systemWatch the pressure gauge on the front of the boiler until the needle reaches the green zone (typically 1.0 to 1.5 bar)Close the filling loop valves tightly and ensure the boiler resets

Est. cost
£80-150
Parts
Pressure relief valve, Expansion vessel, Filling loop
Full guide for F.22
03
F.00 High Engineer

Your boiler has stopped working because it is unable to accurately measure the temperature of the water moving through it.

Est. cost
£120-220
Parts
Flow temperature sensor (NTC sensor), Wiring harness
Full guide for F.00
04
F.01 High Engineer

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

Est. cost
£120-200
Parts
Return temperature sensor (NTC thermistor), Wiring harness
Full guide for F.01
05
F.10 High Engineer

Your boiler has stopped working because it is unable to accurately measure the temperature of the water flowing through it due to an electrical connection issue.

Est. cost
£120-200
Parts
Flow temperature sensor, Wiring harness
Full guide for F.10
06
F.11 High Engineer

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

Est. cost
£120-200
Parts
Return temperature sensor, Wiring harness
Full guide for F.11
Parts most often replaced

on the Glow-worm Betacom4

Filling loopPressure relief valveExpansion vesselFlow temperature sensor (NTC sensor)Wiring harnessReturn temperature sensor (NTC thermistor)

Based on parts cited in our fault code database. Your engineer will confirm what's actually needed after diagnosis.

Call a Gas Safe engineer if…

  • You can smell gas or see signs of a leak
  • The Glow-worm shows an Emergency or High severity code
  • The boiler keeps locking out after repeated resets
  • You've tried the DIY checks and the fault hasn't cleared
  • There's visible water leaking from the boiler
  • The flame is yellow or orange instead of blue
Boiler cover options

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.

See the full 38-code list for the Glow-worm Betacom4

Related guides

Boiler losing pressure → No hot water → When to replace → Symptom checker →