F1
FAULT CODE
Glow-worm
Ignition Failure / Lockout
Medium Severity
DIY Check Possible
The boiler has failed to ignite after five attempts and entered lockout. In winter, the most common cause is a frozen condensate pipe.
Cold Weather Note
F1 in cold weather is almost always a frozen condensate pipe. Thaw before calling an engineer.
Step-by-Step Fix Guide
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Step 1
Check gas supply is working
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Step 2
Check the condensate pipe for frost (white plastic pipe on outside wall)
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Step 3
Thaw condensate pipe with warm water if frozen
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Step 4
Reset the boiler once
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Step 5
If the fault persists, call a Gas Safe engineer
Gas Safe Reminder
Work on gas appliances must be carried out by a Gas Safe registered engineer. The steps above cover safe checks a homeowner can perform - any internal component replacement requires a qualified professional. If in doubt, always call an engineer.