F.33
Glow-worm fault code
Glow-worm F.33: air pressure switch fault (fan frost protection active)
Engineer only
Glow-worm describes F.33 on Energy range boilers as: air pressure switch fault (fan frost protection active). Possible causes Glow-worm lists, for an engineer to check: pressure monitor defective, blocked pipe, insufficient air.
What you can safely do
There is nothing you can safely do yourself with this one. Leave the boiler off and book an engineer.
Call a Gas Safe engineer if
- Book a Gas Safe registered engineer.
Find a Gas Safe engineer near you
Opens the official Gas Safe Register search.
Applies to: Energy range. Codes can differ between models, so check your manual.