How to Fix Glow-worm F75 Fault Code (UK)
Glow-worm showing F75 — Pump/sensor. UK diagnosis, likely spare (pump 0020020023) and step-by-step reset.
Glow-worm
What the code means
F75 on a Glow-worm indicates pump/sensor. The boiler locks out to protect the heat exchanger and, on gas faults, to comply with the Gas Safety (Installation and Use) Regulations. Always reset to confirm the code is live, not historical.
Likely spare
The most common fix is the pump 0020020023. Check the exploded diagram against the GC number on the data plate before ordering — Glow-worm revised parts on Glow-worm units mid-production.
Fix procedure
Check PWM lead.
Log the fault and reset. If the code returns within 24 hours, escalate to full electrical diagnosis with a manometer and multimeter.
Frequently asked questions
- Can I reset F75 myself?
- You can press the reset button up to 3 times. If F75 returns, the boiler needs a Gas Safe engineer — it is illegal to repair gas components without registration.
- Is the part covered under warranty?
- Glow-worm standard warranty is 2–10 years depending on model. Registered installations get the full term. Check the sticker inside the case.
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