Same-day repairs on every Glow-worm model — Energy, Ultimate, Betacom and older Micron ranges — by Gas Safe engineers who understand the Vaillant-group internals shared across the range. Common parts on the van, one-visit fixes wherever the parts allow.
Common Glow-worm codes we clear daily
F1
F4
Average reply under 10 minutes. No obligation.
Glow-worm is part of the Vaillant Group, which is why many of its faults and error codes look familiar — the internals share design DNA with Vaillant ecoTEC. Across London we see F1 low-pressure lockouts (usually a slow leak on the system, not the boiler itself), F4 flame-loss faults on ageing ignition electrodes, and F22 pressure switch or sensor issues on units that have never been properly serviced.
The upside is strong parts availability and long-lived heat exchangers on the Ultimate and Energy ranges. Combine a repair with a magnetic filter and an annual service and most Glow-worms will run cleanly for another decade.
Repressurise to 1.5 bar. Recurring F1 means a leak — book a trace, don’t keep topping up.
F4
Often ignition electrode wear or a gas supply issue. Engineer only.
Showing a different code? Call 020 3000 0000 and read it to us — we’ll tell you what it means over the phone, free.
If your Glow-worm is over 12 years old and facing a major repair, we’ll give you honest repair-vs-replace numbers on site — see our new boiler installation options.
Diagnostic visit
F1 repressurise + leak trace
Fixed quote before work begins, 12-month workmanship guarantee, genuine or manufacturer-approved parts.
— THORNTON HEATH
Many core components are shared or very close cousins, which is why parts availability and diagnostic paths are similar. Our engineers work on both every week.
Yes — genuine or manufacturer-approved parts, which protects any remaining warranty.
