Potterton E384 Fault Code: Causes, Fixes & Repair Costs
What does the Potterton E384 fault code mean?
The E384 fault code appears on Potterton boilers when the PCB detects a flame signal at a point when the gas valve should be closed and no flame should be present. In other words, the boiler's control board is registering combustion activity that it doesn't expect — a so-called 'false flame' signal. Because this involves the gas circuit behaving unpredictably, the boiler will lock out as a safety precaution. This fault must be treated seriously: if your boiler has not locked itself out automatically, switch it off at the isolator and contact a Gas Safe registered engineer without delay. Do not attempt repeated resets — this will not resolve the underlying issue and could be unsafe.
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 or sticking gas valve Common
The gas valve controls the flow of gas into the burner. If it sticks in the open position or fails to close fully when commanded, gas can continue to reach the burner after the call for heat has ended, causing the flame sensor to detect combustion when it shouldn't. A Gas Safe engineer can test the valve's operation and determine whether it can be serviced or needs replacing.
- Flame sensor fault or contamination Common
The flame sensor (also called the ionisation probe) reads the presence or absence of a flame during operation. If this component is dirty, degraded, or failing, it can generate a spurious flame signal even when the burner is off — leading the PCB to log E384. An engineer will clean and test the probe and replace it if necessary.
- Wiring fault or incorrect polarity Common
Loose, damaged, or incorrectly connected wiring between the PCB, gas valve, and flame sensor can produce misleading electrical signals. Internal boiler vibration over time can cause connections to work loose. Incorrect polarity in the mains supply wiring is another known trigger. An engineer will inspect the full wiring harness and use a multimeter to verify correct voltage and polarity throughout.
- PCB fault Sometimes
If the control board itself is malfunctioning — for example due to a component failure or moisture damage — it may misinterpret or generate false signals, including a spurious flame detection reading. The PCB is usually considered after other components have been ruled out, as it is the most expensive part to replace.
- Water ingress or internal leak Sometimes
A leaking pump seal, cracked heat exchanger, or failed pipe joint inside the boiler casing can allow water to reach electrical components. Moisture on the PCB or wiring connections can cause erratic sensor readings including false flame signals. An engineer will always check for signs of water damage — typically evidenced by corrosion or burnt-looking connections — before replacing electrical parts.
How to fix it
- Switch off the boiler if it has not already locked out DIY safe
If your boiler is displaying E384 but has not locked out automatically, turn it off at the boiler's power switch or isolate it at the fused spur. Do not leave it running with this fault active, as it relates to unexpected gas valve behaviour.
- Do not attempt repeated resets DIY safe
You may try a single reset following your boiler's user manual instructions — typically holding the reset button for a few seconds. If the fault returns immediately or after a short time, do not reset again. Repeated resets will not fix the underlying cause and may be unsafe with a false flame fault.
- Check that your gas supply is working DIY safe
Confirm that other gas appliances in your home (such as a hob or gas fire) are functioning normally. If you have no gas at all, contact your gas supplier. If gas is available elsewhere but the boiler fault persists, the issue is internal to the boiler.
- Call a Gas Safe registered engineer for diagnosis Gas Safe engineer
An engineer will carry out a visual inspection of the boiler internals, check for water damage or burnt wiring, test the flame sensor, verify the wiring polarity and connections with a multimeter, and assess the gas valve operation. Only a Gas Safe registered engineer is legally permitted to work on the gas valve or any part of the gas circuit.
- Gas valve inspection and service or replacement Gas Safe engineer
The engineer will test whether the gas valve is closing correctly when commanded. A sticking valve may sometimes be freed and refitted if it is in good condition, but a faulty valve will need to be replaced. This is gas component work and must not be attempted by anyone without Gas Safe registration.
- Flame sensor cleaning or replacement Gas Safe engineer
If the ionisation probe is found to be contaminated or degraded, the engineer will clean it or fit a replacement. This is a relatively low-cost fix if no other components are involved.
- Wiring inspection and correction Gas Safe engineer
The engineer will inspect all relevant wiring for loose terminals, damaged insulation, or incorrect polarity, re-securing or replacing as needed. This work involves internal boiler electrics and must be carried out by a qualified engineer.
- PCB replacement if required Gas Safe engineer
If all other components test correctly, a faulty PCB may be the root cause. The engineer will fit a replacement control board. Given the cost involved, it is worth asking the engineer to assess the overall condition of the boiler at the same time to establish whether further components are likely to fail soon.
Parts you may need
- Gas valve · from £150
- Flame sensor / ionisation probe · from £25
- PCB (printed circuit board) · from £220
- Wiring harness · from £40
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 £250–£450, depending on the underlying cause.
Frequently asked questions
Is the Potterton E384 fault dangerous?
It should be treated as a serious fault. A false flame signal means the boiler's PCB is detecting combustion when the gas valve should be off, which points to unpredictable gas valve behaviour or a faulty sensor. If the boiler has not locked out automatically, switch it off immediately and call a Gas Safe engineer. Do not keep resetting it.
Can I reset my boiler to clear the E384 code?
A single reset is worth trying, but if the fault returns straight away or after a short time, stop there. Resetting repeatedly will not fix the underlying problem and with a false flame fault it is not safe to do so. The root cause — whether a sticking gas valve, faulty flame sensor, or wiring issue — needs to be diagnosed and repaired by a Gas Safe registered engineer.
How much does it cost to fix a Potterton E384 fault?
Most people with this fault pay somewhere between £250 and £450 all-in, depending on which component is at fault. A flame sensor replacement is at the cheaper end; a gas valve replacement typically costs around £300 including labour; a full PCB replacement can reach £400–£500. If the boiler has water damage or multiple components need attention, costs can be higher — in which case your engineer may recommend comparing the repair cost against a new boiler installation.
Why has my Potterton boiler developed an E384 fault?
The most common triggers are a gas valve that is sticking or not closing fully, a dirty or degraded flame sensor giving a false reading, or a wiring fault such as a loose connection or incorrect polarity. Less commonly, moisture from an internal leak reaching the PCB or wiring can cause erratic sensor signals. An annual boiler service helps catch these issues early — keeping connections clean and tight, and spotting deteriorating components before they cause a lockout.