Boiler
E6
The E6 error code on a Glow-worm boiler indicates a fault with the fan or flue gas sensing circuit — it’s a safety lockout that stops your boiler firing until the issue is resolved. This is not a minor glitch; your boiler will not produce heat or hot water until the fault is cleared.
What does this error mean?
The E6 code tells you that your Glow-worm boiler’s control board has detected a problem with the fan speed or the air pressure/flue sensing system. The boiler uses a fan to push combustion gases safely out through the flue, and a pressure switch to confirm this is happening correctly. When the signal from that system falls outside the expected range, the boiler locks out to prevent unsafe combustion gases building up inside your home.
Est. repair cost
£80–£350 for professional repair depending on the faulty component (fan, pressure switch, or PCB). No safe DIY fix for this fault.
🔍 Likely causes
🛠️ Step-by-step fix
Step 1 — Reset the boiler: Press and hold the reset button (usually marked with a flame or ‘R’ symbol) for 3–5 seconds. Wait 2 minutes to see if the boiler fires up normally. This can clear a temporary lockout.
Step 2 — Check the external flue terminal: Go outside and visually inspect the flue outlet (usually a white plastic pipe on an external wall or roof). Look for obvious blockages such as leaves, debris, or a bird nest. Do not attempt to dismantle the flue yourself.
Step 3 — Check your condensate pipe hasn’t frozen: In cold weather, the condensate pipe (a white plastic pipe that exits the boiler and usually runs to an outside drain) can freeze solid. You can carefully pour warm (not boiling) water over the external section to thaw it, then reset the boiler.
Step 4 — Do not attempt further DIY: The fan, pressure switch, PCB, and internal flue components are all gas-related or safety-critical parts. Working on these yourself is unsafe and illegal without Gas Safe registration. Stop here and call a qualified engineer.
Step 5 — If the boiler resets but locks out again within hours: Do not keep resetting repeatedly. A recurring E6 fault means a component needs professional diagnosis and replacement. Note how quickly it returns after reset — this helps the engineer diagnose the fault faster.
📞 When to call a professional
Call a Gas Safe registered engineer if the boiler fails to stay running after a reset, or if you can see no obvious external blockage at the flue terminal. Tell the engineer: ‘My Glow-worm boiler is showing an E6 error code — I believe it’s a fan or air pressure fault.’ This gives them the right context to bring the likely parts. Do not attempt to remove the boiler casing or touch any internal components yourself.
⚖️ Repair or replace?
A fan replacement on a Glow-worm boiler typically costs £150–£350 all-in with a Gas Safe engineer; a pressure switch is cheaper at £80–£180. If your boiler is over 10–12 years old and facing a fan or PCB fault, repair costs can approach 50% of a new boiler’s price — at that point, replacement is often better value. A new Glow-worm boiler installed costs roughly £1,800–£2,800, and comes with a manufacturer warranty of up to 10 years.