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Glow-worm Boiler Repair: Getting an Engineer Out
For Glow-worm boiler repair, an engineer can come out day or night for the £60 call-out, check the gas supply, flue and condensate route, then test the part behind the lockout and agree the repair price with you before any work starts. Low pressure and a frozen condensate pipe you can often sort yourself.
What the visit covers
- Older ranges such as the Flexicom and the original Ultracom cxi, sxi and hxi
- Newer ranges such as Energy and Ultracom2
- Ignition failure and flame loss lockouts
- Pressure faults, pressure sensors and pumps
- Making the boiler safe tonight if a part has to be ordered
Reading a Glow-worm fault before the engineer arrives
Glow-worm is part of the same group as Vaillant, and its boilers use two code styles. Older ranges such as the Flexicom and the original Ultracom cxi and sxi show plain codes like F1 or F9. Newer ranges, including Energy and Ultracom2, use the Vaillant-style format with a dot, such as F.22 or F.28. The same number can mean different things in the two systems, so read the display carefully and check the model name on the front before looking a code up.
- F1 (older models): ignition fault. The boiler tried to light, saw no flame and locked out.
- F9 (older models): a water pressure fault, which can be low pressure, the pressure sensor, a blocked flow filter or the pump.
- F.22 (newer models): safety shut-down because water pressure in the boiler is too low.
- F.28 (newer models): ignition failed on start-up.
- F.29 (newer models): the flame went out while the boiler was running.
- F.75 (newer models): the boiler did not sense the pressure change it expected when the pump started, which points to the pressure sensor or the pump.
The Glow-worm fault codes section goes through each code in more depth. Your boiler manual has the definitive list for your model.
Glow-worm boiler not working: safe checks first
For a pressure code, look at the gauge. If it is under 1 bar, top up with the filling loop to about 1.5 bar cold and close the valves fully. Our guide to Glow-worm boiler pressure shows where the filling loop sits on the common models. If the pressure keeps falling, the boiler is losing water somewhere and needs looking at.
For an ignition code, first check a prepayment gas meter has credit and that the hob lights. In cold weather, check the condensate pipe outside. Glow-worm condensing boilers shut down when that pipe freezes because the water has nowhere to go. Warm it with warm, not boiling, water and reset once. If the code comes back, or it is not freezing outside, the cause is inside the boiler.
Nothing inside the casing is a householder job. If you smell gas, open windows, turn off at the meter if it is safe to, avoid switches, then leave and call the National Gas Emergency Service on 0800 111 999.
What the engineer does on a Glow-worm repair
On the newer models we read the stored fault history and use it to separate a one-off from a pattern. For ignition and flame loss codes we check gas pressure at the valve, the flue, the condensate trap and then the ignition and flame-sensing electrode. For F9, F.75 and similar pressure faults we check the system pressure, the pump, the pressure sensor and any flow filter before replacing anything. Diverter valves and pumps are the other common wear parts on Glow-worm combis.
If the boiler is still under its manufacturer warranty, contact Glow-worm first, as warranty repairs usually go through them. Gas work is carried out by Gas Safe registered engineers.
How much does a Glow-worm boiler repair cost?
The £60 call-out covers the visit at any hour, and the repair price is agreed with you on site before any work starts. For comparison, published UK cost guides put typical market prices, parts and labour, at around £250 to £500 for a diverter valve and £350 to £700 for a circuit board. An electrode or a cleared condensate trap is a much smaller job. None of those figures are our prices; the pricing page explains how we charge.
If the boiler has stopped completely and you need someone tonight, see emergency boiler repair.
How the visit works
Tell us the model and code
The name on the front panel and exactly what the display shows, dot included.
Engineer tests the fault
Supply, flue and condensate first, then the component the code points to.
Price agreed, then the repair
The repair price is agreed with you on site before any work starts.
Glow-worm fault codes we fix
Questions people ask
How do I reset a Glow-worm boiler?
Press the reset button on the front control panel. Its position and symbol vary by model, so check your user instructions. Press it once and wait for the boiler to try again. If the code returns, do not keep resetting.
What does F1 mean on a Glow-worm boiler?
On older Glow-worm models, F1 is an ignition fault: the boiler tried to light, saw no flame and locked out. A prepayment meter out of credit or a frozen condensate pipe are common causes; otherwise it points to gas supply, the electrode or the gas valve.
Is F.22 the same as F9?
Not quite. F.22 on newer boilers means the water pressure is too low. F9 on older boilers is broader: low pressure is the usual cause, but it can also point to the pressure sensor, a blocked flow filter or the pump. Top up first; if either code returns, it needs an engineer.
Are Glow-worm parts easy to get?
Common parts such as electrodes, pumps and diverter valve parts are widely stocked by UK heating merchants. Less common parts for older models can take longer, in which case the boiler is left safe until the part arrives.