Baxi E384 Fault Code: Causes, Fixes & Repair Costs
What does the Baxi E384 fault code mean?
The E384 code appears when a Baxi boiler detects what it believes to be an active flame even though the gas valve has been commanded off. Because the boiler's control system expects no flame signal at that moment, it treats the reading as a potentially dangerous anomaly and locks the boiler out as a precaution. The boiler will not restart until the fault is cleared and, where necessary, the underlying component is repaired or replaced. This is a safety lockout — do not attempt to bypass it or keep resetting the boiler repeatedly.
General guidance only — not a substitute for professional advice, and not certified by a Gas Safe engineer. Always have your specific appliance assessed by a qualified professional. Any gas work must be carried out by a Gas Safe registered engineer. If you smell gas or suspect carbon monoxide, leave the property and call the National Gas Emergency line on 0800 111 999.
Common causes
- Faulty flame sensor or ionisation electrode Common
The ionisation electrode reads the electrical signal produced by a live flame. If the electrode is worn, contaminated with carbon deposits, or cracked, it can send a misleading current to the PCB even after the gas valve has closed. This is the most frequent root cause of E384 on Baxi boilers.
- Gas valve fault Common
If the gas valve is not closing fully — due to wear, debris, or an internal electrical fault — a small amount of gas can continue to burn after the valve is told to shut. The boiler correctly detects this residual flame and triggers E384. A faulty valve solenoid or valve-to-PCB wiring connection can produce the same effect.
- PCB or internal wiring fault Sometimes
The printed circuit board coordinates the gas valve and the flame sensing circuit. A failing PCB, a damaged relay, or loose wiring between the board and the ionisation circuit can cause the board to misread the flame signal, triggering E384 even when the burner is genuinely off.
- Faulty gas and air unit Sometimes
On some Baxi models the gas and air unit (which manages the mixture delivered to the burner) can malfunction in a way that produces residual combustion or erratic flame signals, confusing the boiler's monitoring system into logging a false flame condition.
- Frozen or blocked condensate pipe Rare
In cold weather, a frozen condensate pipe prevents proper drainage and can cause the boiler to misfire or behave unpredictably. While not a direct cause of a false flame signal, it can contribute to ignition instability that leads to E384 being logged, particularly in winter.
How to fix it
- Check your gas supply is active DIY safe
Make sure your gas meter is on and that other gas appliances in your home (such as a hob or gas fire) are working normally. If there is no gas supply to the property, contact your gas supplier rather than an engineer.
- In winter, check and thaw the condensate pipe if frozen DIY safe
Locate the white plastic condensate pipe that exits the boiler and runs to an external drain. If it feels solid or has ice visible, pour warm (not boiling) water along its length to thaw it, or apply a hot-water bottle. Once thawed, try a reset before calling anyone out.
- Attempt a single boiler reset DIY safe
On most Baxi models, turn the selector dial or hold the reset button as described in your user guide (typically holding the reset position for around 5 seconds). Do this once only. If E384 returns immediately or within a short time, do not reset again — a persistent false-flame fault requires professional diagnosis.
- Call a Gas Safe registered engineer to inspect the flame sensor and ionisation circuit Gas Safe engineer
An engineer will remove and inspect the ionisation electrode for cracking, contamination, or incorrect gap. They will measure the ionisation current with appropriate test equipment and replace the electrode or lead if readings are outside specification.
- Have the gas valve tested and replaced if faulty Gas Safe engineer
Only a Gas Safe engineer may test and replace the gas valve. They will verify the valve closes fully, check solenoid resistance, and inspect the valve-to-PCB wiring loom for corrosion or loose connections. A faulty valve must be replaced — it cannot safely be repaired in situ.
- Have the PCB inspected if other components test satisfactory Gas Safe engineer
If the flame sensor and gas valve are both found to be functioning correctly, the engineer will turn attention to the PCB. Relay faults or failed components on the board can cause spurious flame signals. PCB replacement is a common resolution when other diagnostics draw a blank.
- If no single faulty component is found, have the gas and air unit evaluated Gas Safe engineer
On certain Baxi models, the gas and air unit can produce erratic combustion behaviour. An engineer familiar with Baxi products will assess whether this assembly is contributing to the fault and advise on replacement.
Parts you may need
- Ionisation electrode (flame sensor) · from £25
- Ignition and ionisation lead set · from £35
- Gas valve assembly (Baxi) · from £120
- PCB (Baxi model-specific) · from £200
The exact spare depends on your boiler's GC number (on the data badge). Check this against the part before buying.
Typical repair cost
Expect to pay roughly £150–£400, depending on the underlying cause.
Frequently asked questions
Is it safe to keep resetting a Baxi boiler showing E384?
No. You should try one reset after checking your gas supply and, in winter, thawing any frozen condensate pipe. If E384 comes back after a single reset attempt, stop resetting and call a Gas Safe engineer. The boiler has locked out for a genuine safety reason — a false flame reading means the control system detected combustion when it expected none — and repeatedly forcing restarts will not fix the fault and could mask a developing issue with the gas valve or burner.
How much does it typically cost to fix a Baxi E384 fault?
Most homeowners pay between £150 and £400 all in, depending on which component has failed. Replacing the ionisation electrode is at the lower end; a new gas valve including labour usually falls in the £200–£350 range. If the PCB turns out to be the culprit, expect costs closer to £300–£500, since Baxi PCBs can be expensive and labour time is longer. Emergency call-out fees and regional labour rates (London is typically higher) will also affect the final bill.
Can E384 appear because of a frozen condensate pipe?
Indirectly, yes. A frozen condensate pipe is the most common cause of Baxi lockouts in winter and can cause erratic ignition behaviour that contributes to fault codes being logged. Thawing the pipe and attempting one reset is always worth doing first in cold weather. However, if E384 persists after the pipe is clear, the root cause is almost certainly the flame sensor, gas valve, or PCB rather than the condensate drain.
Which Baxi models most commonly show E384?
E384 can appear across a wide range of Baxi combi and system boilers, including the 200, 400, 600, Duo-tec, Platinum, and EcoBlue ranges. The underlying cause — a false flame signal detected by the boiler's safety monitoring circuit — is the same regardless of model, though the specific parts involved (electrode type, valve model, PCB variant) differ between ranges. Always quote your full model number and serial number to an engineer so they can bring the correct spares.