Glow-worm is one of the most common boiler brands in UK homes. Below are the Glow-worm fault codes we cover, with what each one means and what you can safely check before calling an engineer.
Glow-worm boiler error codes
- F.00 Flow temperature sensor fault
- F.01 Return temperature sensor fault
- F.10 Flow temperature sensor short circuit
- F.11 Return temperature sensor short circuit
- F.20 Safety switch-off — overheating temperature reached
- F.22 Safety switch-off — low water pressure
- F.23 Temperature difference between flow and return too great
- F.24 Temperature rising too fast
- F.25 Flue gas temperature too high
- F.27 Fault in flame detection
- F.28 Ignition unsuccessful when starting up
- F.29 Flame loss
- F.32 Fan speed outside tolerance
- F.61 Gas valve control fault
- F.62 Gas valve switch-off control fault
- F.63 EEPROM (memory) fault
- F.65 Electronics temperature too high
- F.70 Invalid product code (DSN)
- F.73 Water pressure sensor not connected or short-circuited
- F.75 Pressure sensor fault
Before you call anyone
- Check the pressure gauge. Most combis want 1–1.5 bar when cold. Low pressure is behind a large share of lockouts.
- Check your gas. Do other gas appliances work? Is a prepayment meter in credit?
- In freezing weather, check the condensate pipe — the plastic pipe running outside to a drain. A frozen one is a very common cause of ignition codes.
- Reset once. If the same code comes straight back, stop resetting and call a Gas Safe registered engineer.
Should you repair or replace?
If your boiler is more than 10–12 years old and the repair runs to a few hundred pounds, get a replacement price before you agree to it. Parts for older models also get harder to find.
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