Boiler
E3
The E3 error code on a Baxi boiler indicates an ignition or flame failure fault — the boiler is trying to fire but cannot detect a stable flame. It’s a common fault that can sometimes be resolved with a reset, but often requires a Gas Safe registered engineer.
What does this error mean?
When your Baxi boiler displays E3, it means the boiler attempted to ignite but the flame either failed to establish or cut out almost immediately. The boiler’s control board detects this via the flame sensor (ionisation probe) and locks out the unit as a safety measure. Until the underlying cause is fixed, the boiler will continue to lock out after each attempted restart.
Est. repair cost
£80–£200 for electrode/sensor replacement; £200–£400 for gas valve or PCB repair; full boiler replacement £1,800–£2,800 installed
🔍 Likely causes
🛠️ Step-by-step fix
Check your gas supply first: confirm other gas appliances (cooker, hob) are working. If they’re not, contact your gas supplier — the fault is with your supply, not the boiler.
Reset the boiler: press and hold the reset button (usually marked with a flame or ‘R’) for 3–5 seconds. Allow 2–3 minutes for the boiler to attempt a full ignition cycle.
Check the boiler pressure gauge: if pressure is below 1 bar, top it up via the filling loop to 1–1.5 bar, then attempt a reset. Low pressure can contribute to ignition issues.
Inspect the flue outlet (external wall): ensure it’s not blocked by debris, bird nests, or ice in cold weather. A blocked flue can cause the boiler to shut down mid-ignition.
If the boiler locks out again after 2–3 reset attempts, stop resetting it. Repeated failed ignitions can cause unburnt gas to accumulate. At this point, the fault requires a qualified Gas Safe engineer — do not attempt to open or adjust any internal gas components yourself.
Call a Gas Safe registered engineer and tell them: ‘My Baxi boiler is showing an E3 error code and locking out after ignition attempts.’ This helps them prepare the right parts before arriving.
📞 When to call a professional
Call a Gas Safe registered engineer if the boiler locks out more than twice after resetting, or if you smell gas at any point — in which case, do not reset the boiler, leave the property, and call the National Gas Emergency Service on 0800 111 999 immediately. Tell the engineer the exact error code (E3) and how many times it has locked out, as this helps them diagnose whether the fault is the ignition electrode, flame sensor, gas valve, or PCB.
⚖️ Repair or replace?
A typical E3 repair — replacing an ignition electrode or flame sensor — costs £80–£200 including labour, making repair worthwhile on most boilers under 10 years old. If the fault lies with the gas valve (£200–£350 fitted) or PCB (£250–£400 fitted) and your boiler is over 10–12 years old, replacement often makes better financial sense. A new A-rated combi boiler installed typically costs £1,800–£2,800 in the UK, and will be significantly more efficient than an ageing unit.