Ferroli A01 Fault Code
The A01 fault is the most common Ferroli lockout — the boiler attempted to ignite multiple times but could not establish or confirm a stable flame. It is the Ferroli equivalent of Vaillant F.28, Worcester Bosch E1, and Ideal F1.
What is the Ferroli A01 fault code?
The Ferroli A01 fault is triggered when the PCB initiates a series of ignition attempts and the ionisation probe does not confirm a stable flame within the permitted window. Ferroli boilers typically make three attempts before displaying A01 and locking out. The fault can originate at any point in the ignition chain — gas supply, ignition electrode, ignition lead, gas valve, or ionisation probe — and requires a Gas Safe engineer to diagnose. On Ferroli Modena and DOMIproject models, A01 is the single most frequently reported fault code across South London callouts.
What causes the A01 fault?
A closed meter valve, empty prepayment meter, or work on the local gas network starves the boiler. Always test another gas appliance before calling an engineer for A01.
The ceramic insulator cracks or the electrode tip corrodes over time, preventing a consistent spark from reaching the burner. Ferroli electrode quality varies across model ranges.
Combustion deposits on the probe prevent it detecting the flame. The PCB receives no flame signal and locks out — even if ignition was momentarily successful.
Cracked insulation on the high-voltage lead causes the spark to arc to ground. The electrode never receives the spark.
A partially blocked or slow-opening gas valve provides insufficient gas at the burner during the ignition window. The spark fires but the flame cannot establish.
Dust, debris, or limescale deposits in the burner ports prevent even gas flow, resulting in partial or no ignition. More common on older Modena and DOMIproject units.
What you can safely check yourself
Turn on a gas hob or fire. If nothing works, the supply is the problem — call your gas supplier or check your prepayment meter.
Ensure the emergency control valve at the meter is fully open (handle in line with the pipe). If it was accidentally knocked closed, open it and reset.
Press and hold the reset button for 3 seconds. Allow up to 60 seconds for the ignition sequence. If A01 returns, do not reset again — call a Gas Safe engineer.
Do not reset the boiler more than once if the fault code returns immediately. Repeated resets without diagnosis can mask a worsening fault.
What needs a Gas Safe engineer
- Test ignition electrode spark output and replace if degraded
- Clean or replace the ionisation probe
- Inspect and replace the ignition lead if cracking or arcing
- Measure gas inlet and manifold pressure
- Test gas valve opening speed and replace if sluggish
- Clean the burner if carbon deposits are present
- Check flue for backpressure that could prevent ignition
- Assess repair vs replace on units over 8 years given Ferroli parts lead times
Hard water in South London — Wandsworth, Lewisham, Lambeth, Merton, Southwark, Greenwich, and Bromley — accelerates combustion deposits on the ionisation probe and burner of Ferroli boilers. Thames Water's calcium-heavy supply causes limescale build-up inside the burner assembly on units that miss annual services. A01 is the most frequently booked Ferroli fault across Reion's South London callouts, particularly on Modena and DOMIproject units over 7 years old.
How much does a A01 repair cost?
Costs below are UK averages. Reion provides a fixed quote after the £80 diagnostic visit — no obligation to proceed.
How to reset a Ferroli boiler showing A01
Confirm gas supply is working by testing another gas appliance.
Check the meter emergency control valve is fully open.
Press and hold the reset button for 3 seconds.
Wait for the full ignition sequence — up to 60 seconds.
If A01 returns, do not reset again. Call a Gas Safe engineer.
Gas valve replacement is among the more expensive Ferroli repairs, and parts can take 3–7 days to source from specialist suppliers. On a Ferroli Modena or DOMIproject over 8 years old with A01, Reion will give a clear repair-vs-replace comparison at the diagnostic visit — factoring in the boiler's age, parts lead time, and current installed cost of a replacement unit.
Common questions about the Ferroli A01 fault
What does a Ferroli A01 fault code mean?
Can a Ferroli A01 fault fix itself?
How long does a Ferroli A01 repair take in London?
Should I replace my Ferroli boiler instead of repairing the A01 fault?
Why does my Ferroli A01 fault keep coming back?
Other Ferroli fault codes
Need a Ferroli engineer in London?
Reion is Gas Safe registered (919881), based in South London, and available 24/7. Fixed price after the diagnostic visit — no hidden charges.
