Ferroli A01 Fault Code: Ignition Failure Lockout
The A01 code appears when your Ferroli boiler has attempted to light the burner but failed to establish a flame. As a safety measure, the boiler shuts itself down and locks out — meaning it won't restart until the underlying cause is dealt with and the boiler is manually reset. Because A01 starts with an 'A', it is a hard lockout fault and will not clear on its own, unlike some 'F' codes that reset automatically.
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 Ferroli A01 fault code mean?
The A01 code appears when your Ferroli boiler has attempted to light the burner but failed to establish a flame. As a safety measure, the boiler shuts itself down and locks out — meaning it won't restart until the underlying cause is dealt with and the boiler is manually reset. Because A01 starts with an 'A', it is a hard lockout fault and will not clear on its own, unlike some 'F' codes that reset automatically.
Common causes
- Interrupted or low gas supply Common
If the gas supply to the boiler is cut off, undersupplied, or the meter has run out of credit (on prepayment meters), the burner simply has no fuel to ignite. This is the first thing to rule out as it requires no engineering knowledge to check.
- Dirty or faulty ignition electrode Common
The ignition electrode produces the spark that lights the burner. If it's coated in carbon deposits, cracked, or positioned incorrectly, it won't generate a reliable spark. This is one of the most frequent engineering findings when A01 is diagnosed on Ferroli boilers.
- Dirty or failing flame sensing electrode Common
A separate sensor (or in some models a combined electrode) detects whether the flame has actually ignited. If this component is contaminated or degraded, the boiler's control board never receives confirmation that a flame is present and shuts down — even if ignition did briefly occur.
- Blocked or faulty gas valve Sometimes
The gas valve controls the flow of gas to the burner. If it's stuck, partially blocked, or has failed electrically, gas won't reach the burner in sufficient quantity to sustain ignition. Replacement is a Gas Safe-only job.
- Blocked or obstructed flue Sometimes
On older Ferroli models such as the Sigma 50 and Sigma 60 in particular, debris such as leaves, bird nesting material, or frost build-up can block the flue. The boiler may briefly ignite but extinguish almost immediately as exhaust gases cannot escape. A blowing or puffing sound before shutdown is a tell-tale sign.
- PCB or wiring fault Rare
The printed circuit board orchestrates ignition timing and reads the flame sensor signal. A fault on the PCB — or a loose wiring connection between it and the ignition components — can cause A01 even when the gas supply and electrodes are perfectly fine.
How to fix it
- Check your gas supply is working DIY safe
Try lighting a gas hob or gas cooker. If it lights normally, gas is reaching your home and the problem lies with the boiler itself. If the hob won't light either, contact your gas supplier — the issue is upstream of the boiler and a Gas Safe engineer won't be able to help until supply is restored. On prepayment meters, check you have sufficient credit.
- Check the flue outlet for obvious external blockages DIY safe
Go outside and locate where the flue exits the building — typically a white plastic pipe through an external wall. Look for visible obstructions such as leaves, debris, or a bird nesting against the terminal. Do not attempt to reach inside the flue or dismantle any fittings; simply remove anything blocking the opening from the outside if it's safe to do so.
- Reset the boiler once DIY safe
If your gas supply is confirmed and there are no obvious external blockages, press and hold the reset button (usually labelled 'R' or marked with a reset symbol on your Ferroli's fascia) for 5 to 10 seconds. Allow the boiler to go through its ignition sequence fully before assessing whether it has fired successfully.
- Do not reset the boiler repeatedly DIY safe
If the A01 code returns immediately or after a short time, do not keep pressing reset. Repeated failed ignition attempts can overheat internal components and cause additional damage. Two or three resets maximum — if the fault persists, the boiler needs professional attention.
- Call a Gas Safe registered engineer to inspect ignition components Gas Safe engineer
A qualified engineer will test the ignition electrode for cracks and carbon fouling, check the electrode gap and positioning, test the flame sensing electrode's resistance, and verify that the gas valve is opening correctly and delivering adequate pressure at the burner. These checks involve gas-carrying components and live electrical circuits and must not be attempted by a homeowner.
- Allow the engineer to replace faulty components or carry out further diagnostics Gas Safe engineer
Depending on findings, the engineer may clean or replace the ignition and flame sensing electrodes, replace the gas valve, inspect the PCB and associated wiring, or investigate the flue and combustion air path more thoroughly. All of this work requires Gas Safe registration and appropriate test equipment.
Parts you may need
- Ignition electrode · from £25
- Flame sensing electrode · from £20
- Gas valve · from £130
- PCB (control board) · from £220
- Boiler fan / flue fan · from £95
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 Ferroli A01 code myself?
The only checks a homeowner should carry out are confirming the gas supply is on, looking for obvious external flue blockages, and attempting a single reset. Everything else — cleaning or replacing the ignition electrode, testing the gas valve, or inspecting the PCB — must be done by a Gas Safe registered engineer. Attempting gas-side repairs without registration is illegal and dangerous.
How many times should I reset my Ferroli boiler for an A01 fault?
No more than two or three times in total. If the fault keeps returning after a reset, repeated attempts will not fix the underlying problem and could cause additional wear to internal components such as the heat exchanger. At that point, stop resetting and call an engineer.
How much does it cost to fix a Ferroli A01 fault?
For the most common causes — cleaning or replacing the ignition or flame sensing electrode — you're typically looking at £120 to £250 including labour and parts. If the gas valve needs replacing, costs generally fall in the £250 to £350 range. A PCB replacement is more expensive; the board itself can cost over £200 for some Ferroli models, with an additional £100 to £200 for fitting, so total PCB repair costs can exceed £400. If your boiler is over ten years old and requires a major component, it's worth getting a new boiler quote for comparison.
Why does my Ferroli boiler ignite briefly and then cut out with an A01?
A brief ignition followed by immediate shutdown usually means the flame sensing electrode is not confirming the presence of a flame to the PCB — even though a flame did exist momentarily. This can happen if the sensing electrode is contaminated, positioned incorrectly, or failing. On older Ferroli Sigma models it can also indicate a flue restriction preventing proper combustion; the boiler's safety systems detect abnormal combustion and shut it down. Either way, a Gas Safe engineer needs to investigate.