Boiler
E6
The E6 error code on a Baxi boiler indicates a fan or air pressure fault — specifically a problem with the flue gas exhaust system. It can leave you without heating or hot water and should not be ignored.
What does this error mean?
The E6 code tells you the boiler’s control board has detected an issue with the fan or the air pressure switch (also called the differential pressure switch). These components work together to confirm that combustion gases are being safely expelled through the flue before the boiler is allowed to fire. If the boiler cannot verify safe flue operation, it locks out as a precautionary safety measure to prevent dangerous gas build-up.
Est. repair cost
£80–£350 depending on the faulty component (pressure switch vs. fan motor); PCB replacement £200–£450
🔍 Likely causes
🛠️ Step-by-step fix
Reset the boiler: Press and hold the reset button (usually marked with a flame symbol) for 3–5 seconds. If the boiler fires up and runs normally, monitor it closely for repeat lockouts.
Check the external flue terminal: Go outside and look at where the flue exits your home (usually a white plastic pipe on an external wall or roof). Make sure it is not blocked by leaves, debris, a bird nest, or ice. Do not attempt to dismantle the flue — only clear any obvious external obstruction you can safely reach.
Check the condensate pipe (condensing boilers only): In freezing weather, the external condensate pipe can freeze and block drainage. Carefully pour warm (not boiling) water over the external pipe to thaw it, then reset the boiler.
Inspect the pressure switch hose: This is a visual check only — do not attempt gas-side work. If you can see the boiler’s internal components through an inspection hatch and spot a visibly disconnected or split rubber hose near the fan, note it to report to an engineer.
If the boiler continues to lock out on E6 after a reset and none of the above apply, stop here. The fault is internal and requires a Gas Safe registered engineer — do not attempt further DIY on gas components.
📞 When to call a professional
Call a Gas Safe registered engineer if the E6 code returns after a reset, if you cannot identify an obvious external flue blockage, or if the boiler is making unusual grinding or whirring noises suggesting a fan motor failure. Tell the engineer you have an E6 fault code and that the boiler is locking out — this helps them bring the right parts. Never attempt to dismantle the fan, pressure switch, or any gas components yourself.
⚖️ Repair or replace?
A fan replacement on a Baxi boiler typically costs £150–£350 including parts and labour; a pressure switch is cheaper at £80–£180 all-in. If your boiler is over 10–12 years old and facing a fan or PCB repair, it is worth getting a like-for-like replacement quote — a new A-rated condensing boiler costs £1,500–£2,500 installed and will be significantly more efficient. For boilers under 8 years old in otherwise good condition, repair is almost always the right call.