Potterton E168 Fault Code: Causes, Fixes & Repair Costs
What does the Potterton E168 fault code mean?
The E168 code appears on Potterton boilers when the appliance has entered a lockout state — meaning it has shut itself down to prevent unsafe operation or further damage. Rather than pointing to one specific component failure, E168 is a broad safety-shutdown signal that can follow an unresolved prior fault, a disrupted power supply, an ignition failure, or an internal component problem. Because the boiler's PCB (Printed Circuit Board) is responsible for triggering this lockout, E168 is sometimes referred to as a PCB lockout code, though the root cause is often elsewhere in the system. The same code appears on compatible Baxi and Main boilers that share the same platform.
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
- Unresolved prior fault code Common
The boiler may have previously displayed a different error code, been reset (manually or automatically), and then been unable to confirm the original fault on restart. In this situation it falls back to E168 as a catch-all lockout. Checking the boiler's history for earlier codes is an important first diagnostic step for any engineer.
- Unstable or interrupted mains power supply Common
E168 can be triggered when the voltage supplied to the boiler strays more than roughly 10% away from the required 230 V. Power cuts, fluctuating mains voltage, or loose electrical connections inside or outside the boiler can all cause this. Because the fluctuation may only happen at certain times of day, it can be tricky to catch without monitoring equipment.
- Ignition or flame detection failure Sometimes
If the boiler cannot achieve a stable flame — due to dirty or worn ignition electrodes, a faulty flame sensor, or carbon build-up on the sensing rod — it will lock out and display E168. This is one of the more straightforward faults for an engineer to diagnose and often resolves with a clean or replacement of the electrode assembly.
- Internal component failure or water ingress Sometimes
Leaks inside the boiler casing can allow water to reach electrical components, causing shorts or signal errors that result in a lockout. Other internal components such as the gas valve, sensors, or wiring harness may also degrade over time and trigger E168 without generating a more specific code.
- Faulty or damaged PCB Rare
The PCB coordinates every function in the boiler. If it has been damaged — by a power surge, age, moisture, or a manufacturing defect — it can misread sensor data or fail to process signals correctly, producing an E168 lockout even when other components are healthy. PCB failure tends to be a last-resort diagnosis after everything else has been ruled out.
How to fix it
- Reset the boiler once or twice via the control panel DIY safe
Locate the reset button on the boiler's fascia and hold it for roughly 3–5 seconds until the boiler attempts to restart. A single reset is worth trying, and a second attempt is reasonable if the first fails — but do not keep resetting repeatedly, as this can mask a serious underlying problem or cause additional damage.
- Check whether earlier fault codes were displayed before E168 appeared DIY safe
Think back to whether the boiler showed a different error code in the days or weeks before E168. If so, note that code and search for its meaning — resolving the original fault may clear the E168 lockout. Pass this information to your engineer, as it significantly speeds up diagnosis.
- Confirm the gas supply to the property is active DIY safe
Check that other gas appliances in the home (such as a gas hob) are working normally. If they are not, contact your gas supplier rather than an engineer, as the issue is with the supply rather than the boiler.
- Inspect the mains electrical supply to the boiler DIY safe
Ensure the boiler's isolator switch is in the on position and that the relevant circuit breaker in your consumer unit has not tripped. If you notice any signs of scorching, burning smells, or tripped breakers that keep returning, contact a qualified electrician — do not reset a repeatedly tripping breaker yourself.
- Engineer inspection: check and clean ignition electrodes and flame sensor Gas Safe engineer
A Gas Safe engineer will remove the electrode assembly and flame sensor, inspect them for carbon deposits, corrosion, or physical damage, and clean or replace them as needed. This is a relatively quick job and is often carried out as part of a boiler service. Correct electrode gap and alignment will also be verified.
- Engineer inspection: test the mains voltage and internal wiring Gas Safe engineer
Using appropriate test equipment, the engineer will measure the incoming supply voltage and check internal wiring looms, connectors, and terminals for signs of corrosion, looseness, or water damage. Any faulty wiring will be repaired or replaced.
- Engineer inspection: test individual internal components Gas Safe engineer
The gas valve, pressure sensors, thermistors, and other internal components will be tested in turn to identify any that are operating outside their normal parameters. This systematic approach avoids the costly mistake of replacing the PCB when another, cheaper component is actually at fault.
- Engineer repair or replacement of faulty components, including PCB if necessary Gas Safe engineer
Once the root cause has been identified, the engineer will carry out the appropriate repair — which may be as straightforward as fitting new electrodes or as involved as replacing the gas valve or PCB. PCB replacement is generally treated as a last resort after all other components have been assessed and cleared.
- Call a Gas Safe registered engineer if the fault persists after resetting Gas Safe engineer
If the boiler returns to E168 lockout after one or two resets, or if you have any doubt about the cause, contact a Gas Safe registered engineer to carry out a full diagnostic inspection. Do not attempt to open the boiler casing or interfere with any internal parts — doing so is dangerous and may also void any remaining warranty.
Parts you may need
- Ignition electrode assembly · from £35
- Flame sensor / detection rod · from £25
- Ignition lead set · from £20
- Gas valve · from £120
- PCB (printed circuit board) · from £220
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 £120–£380, depending on the underlying cause.
Frequently asked questions
Is E168 always a PCB fault on a Potterton boiler?
Not necessarily. E168 is sometimes called a PCB lockout code because the PCB is what triggers the shutdown, but the underlying cause is frequently something else entirely — a power supply issue, dirty ignition electrodes, or an unresolved earlier fault. A Gas Safe engineer will work through the likely causes systematically before concluding the PCB itself needs replacing. Jumping straight to a PCB replacement without proper diagnosis risks spending several hundred pounds unnecessarily.
How much does it cost to fix a Potterton E168 fault?
For the most common causes — cleaning or replacing ignition electrodes and the flame sensor — expect to pay roughly £80 to £180 including labour. If the gas valve needs replacing, costs typically fall in the £200 to £350 range. Most E168 repairs land somewhere between £120 and £380. PCB replacement is the expensive outlier: parts and labour together can reach £450 to £700, which is why engineers treat it as a last resort. If your boiler is older and the PCB has failed, it may be worth comparing that cost against a new boiler installation.
Can I keep resetting my Potterton boiler to clear E168?
One or two resets are fine as a first step, but you should not keep resetting the boiler if it keeps returning to lockout. Repeated resets without fixing the root cause can put additional strain on components and, in some situations, create a safety risk. If the boiler locks out again after a couple of attempts, treat it as a sign that professional diagnosis is needed.
Which Potterton boiler models can show the E168 code?
E168 is reported on eight Potterton models: the Heatmax Combi HE, Promax Combi HE Plus, Promax System HE Plus, Promax System HE Plus A, Gold Combi HE, Gold Combi HE A, Gold System HE, and Gold System HE A. The same code also appears on certain Baxi and Main boilers that share the same control platform, so if you have one of those brands and see E168, the same diagnostic approach applies.