Vokera A01 Fault Code: Ignition Failure / Flame Not Detected
The A01 code appears when your Vokera boiler attempts to light the burner but either fails to ignite or cannot confirm that a stable flame has been established. As a safety precaution, the boiler shuts itself down into lockout mode to stop unburned gas from building up. Until the underlying problem is resolved, the boiler will refuse to fire for heating or hot water.
General guidance only — not a substitute for professional advice. 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.
What does the Vokera A01 fault code mean?
The A01 code appears when your Vokera boiler attempts to light the burner but either fails to ignite or cannot confirm that a stable flame has been established. As a safety precaution, the boiler shuts itself down into lockout mode to stop unburned gas from building up. Until the underlying problem is resolved, the boiler will refuse to fire for heating or hot water.
Common causes
- Faulty or dirty flame sensor Common
The flame sensor (also called an ionisation probe) tells the PCB whether a flame is actually present after ignition. If it is coated in oxidation or carbon deposits, or has developed a fault, it may report no flame even when one exists — or vice versa. This is the first component a Gas Safe engineer will test when an A01 appears.
- Worn ignition electrode or lead Common
The spark electrode and its connecting lead generate the spark that lights the burner. Over time, the ceramic insulation can crack, the electrode tip can erode, or the lead can develop breaks that weaken or prevent the spark. Moisture ingress after a cold spell can also cause temporary failure. A multimeter check will confirm whether the components are delivering adequate voltage.
- Gas supply interrupted or low pressure Common
If the gas meter isolator valve is closed, a prepayment meter has run out of credit, or the gas network is experiencing a supply interruption, the burner simply cannot light. Other gas appliances in the property — such as a hob or gas fire — will also fail to work if this is the cause.
- Frozen condensate pipe Sometimes
During cold weather, the condensate pipe that runs outside the property can freeze solid, blocking drainage and causing the boiler to lock out. Although the A01 is primarily an ignition code, a frozen condensate can prevent the boiler from completing its startup sequence on some Vokera models.
- Sticking or failed gas valve Sometimes
The gas valve controls how much gas reaches the burner. Over years of use, the valve can stick partially closed, restricting gas flow to the point where ignition is inconsistent or impossible. If the electrode, lead, and flame sensor have all been ruled out, the gas valve is the next suspect.
- PCB (printed circuit board) fault Rare
The PCB coordinates every stage of the ignition sequence — sending signals to the gas valve, triggering the spark, and reading the flame sensor response. If the board itself is faulty, it may send incorrect signals or misinterpret sensor readings, causing a persistent A01 even after other parts have been replaced.
How to fix it
- Check that other gas appliances are working DIY safe
Turn on a gas hob ring or check a gas fire if you have one. If nothing gas-powered works in the property, the issue is with your gas supply rather than the boiler. Contact your gas supplier or check your prepayment meter credit before doing anything else.
- Inspect your prepayment meter credit DIY safe
Many overnight A01 faults occur simply because a pay-as-you-go gas meter has run out of credit. Top up and wait a few minutes for gas to reach the boiler before attempting a reset.
- Check system pressure is within range DIY safe
Look at the pressure gauge on the front of the boiler — it should read between 1 and 1.5 bar when the system is cold. If it is below 0.5 bar, top it up using the filling loop beneath the boiler until it reaches around 1.2 bar, then close the filling loop valves fully.
- Thaw a frozen condensate pipe (winter only) DIY safe
If the weather is below freezing and your condensate pipe runs outside, it may be blocked with ice. Carefully pour warm (not boiling) water along the length of the exposed pipe, working from the boiler end outward. Alternatively, wrap a hot-water bottle around the frozen section. Once thawed, attempt a reset.
- Reset the boiler once DIY safe
On most Vokera models, turn the mode selector dial to the OFF/RESET position and hold it there for 5–10 seconds, then return it to your preferred heating or hot water setting. If your model has a dedicated reset button marked R, press and hold it for 3–5 seconds. Only attempt this once or twice — repeated resets will not fix an underlying fault and can cause additional wear to components.
- Call a Gas Safe registered engineer if the fault returns Gas Safe engineer
If the A01 code reappears after a reset, stop resetting and book a Gas Safe registered engineer. They will test the flame sensor with the appropriate equipment, inspect the ignition electrode and lead for wear or moisture damage, check gas pressure at the burner, and assess the gas valve and PCB. It is a legal requirement in the UK that all gas boiler repair work is carried out by a Gas Safe registered professional.
Parts you may need
- Ignition electrode (spark probe) · from £25
- Ignition lead (HT lead) · from £30
- Flame sensor / ionisation probe · from £20
- Gas valve · from £120
- PCB (printed circuit board) · 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 £120–£350, depending on the underlying cause.
Frequently asked questions
Can I fix the Vokera A01 fault code myself?
A few preliminary checks are safe to do yourself — confirming your gas supply is on, topping up your prepayment meter, checking system pressure, thawing a frozen condensate pipe, and attempting a single reset. Beyond that, all diagnostic and repair work must be carried out by a Gas Safe registered engineer. Working on gas components without registration is illegal and dangerous.
Why does my Vokera boiler keep showing A01 after I reset it?
If the fault returns immediately or within a short time of resetting, there is an underlying component failure that a reset cannot cure. The most likely culprits are a degraded flame sensor, a worn ignition electrode or lead, or a faulty gas valve. Continuing to reset without fixing the root cause can cause additional damage. Book a Gas Safe engineer to diagnose and repair the fault properly.
How much does it cost to fix a Vokera A01 fault in the UK?
Most A01 repairs fall between £120 and £350 including parts and labour. Replacing an ignition electrode and lead together typically costs around £150–£200, while a flame sensor swap is usually £100–£150. A gas valve replacement tends to sit around £250–£350 all in. PCB replacement is less common but significantly more expensive — potentially £400–£500 — and on an older Vokera boiler it may be worth comparing that cost against a new boiler quote.
Could a frozen condensate pipe cause a Vokera A01 error?
Yes, it can — particularly during cold snaps. Some Vokera models will lock out with an A01 if the condensate drainage is blocked by ice, because the boiler cannot complete its startup sequence safely. The fix is straightforward: pour warm (not boiling) water along the external pipe to thaw it, then reset the boiler. To prevent it happening again, consider insulating the exposed section of pipe with foam lagging before the next winter.