Boiler
E128
The E128 error code on a Baxi boiler indicates a fan-related fault — specifically a problem with the fan speed or signal, and it will lock out your boiler until the issue is resolved. This is a moderately serious fault that almost always requires a Gas Safe registered engineer.
What does this error mean?
The E128 code means your Baxi boiler’s PCB (main circuit board) is not receiving the correct speed signal from the flue fan. The fan is critical for safe combustion — it expels harmful gases like carbon monoxide out of your home. When the boiler cannot confirm the fan is running at the right speed, it shuts down as a safety precaution.
Est. repair cost
£150–£300 for fan replacement; £250–£450 for PCB replacement (parts + Gas Safe labour)
🔍 Likely causes
🛠️ Step-by-step fix
Step 1 – Reset the boiler: Press and hold the reset button (usually marked with a flame and a cross) for 3–5 seconds. Wait 2 minutes and see if the boiler fires up normally. A one-off lockout can sometimes be cleared this way.
Step 2 – Check the flue terminal outside: Look at where the flue exits your external wall. Clear any visible blockages such as bird nests, debris, ice, or vegetation. Never obstruct or modify the flue.
Step 3 – Check your gas supply: Confirm other gas appliances (hob, fire) are working to rule out a wider gas supply issue. If you have a prepayment meter, check your credit.
Step 4 – Do not attempt further DIY: The fan, wiring, PCB, and internal flue components on a gas boiler must only be inspected and replaced by a Gas Safe registered engineer. Do not open the boiler casing or attempt to test or replace the fan yourself.
Step 5 – Call a Gas Safe engineer: If the reset does not clear the fault within one or two attempts, book a qualified engineer. Repeated lockouts indicate an underlying component failure that will not self-resolve.
📞 When to call a professional
Call a Gas Safe registered engineer if the E128 error returns after a reset, or if the boiler fails to fire at all. Tell them you have an E128 fan speed fault on your Baxi boiler — this helps them bring the right parts. If you smell gas at any point, do not attempt a reset: leave the property, call the National Gas Emergency Service on 0800 111 999 immediately.
⚖️ Repair or replace?
A fan replacement on a Baxi boiler typically costs £150–£300 including parts and labour; a PCB replacement costs £250–£450. If your boiler is over 10–12 years old and facing a repair bill above £300, replacing the unit is usually better value — a new A-rated Baxi boiler costs £1,800–£2,800 fully installed. For a boiler under 8 years old still under warranty, contact Baxi directly on 0330 678 0917 before booking an independent engineer.