Ferroli Boiler Fault Codes
Gas Safe registered fault diagnosis for Ferroli Modena, DOMIproject, DOMIcompact, and BlueHelix models. A01, A03, A06, A09, A02 — explained with repair costs and honest replace guidance.
Understanding Ferroli boiler fault codes
Ferroli is an Italian manufacturer at the budget end of the UK market. Common in older South London properties and some buy-to-let stock. Fault rates are higher than tier-1 brands and specialist Ferroli parts can take longer to source. Reion repairs Ferroli boilers but will give an honest repair-vs-replace assessment — particularly on units over 8 years old where parts cost may approach new boiler value.
This guide covers the five most commonly searched Ferroli fault codes, with technical explanations of what each fault means, what causes it, and what a Gas Safe engineer will do to fix it. Reion Miller (Gas Safe 919881) handles Ferroli boiler repairs across South London.
Ferroli fault codes explained
Ignition lockout
The boiler could not establish a stable flame after multiple ignition attempts. The most common Ferroli fault, requiring a Gas Safe engineer to diagnose.
Low water pressure
System pressure has dropped below the operating threshold. A03 is the most homeowner-accessible Ferroli fault — usually resolved by repressurising to 1.2–1.5 bar.
Fan / APS fault
The PCB cannot confirm the fan is running at the correct speed, or the air pressure switch has not triggered. Prevents ignition as a flue safety measure.
Flue / overheat sensor fault
The flue gas thermostat or high limit thermostat has tripped, indicating a potential overtemperature condition or sensor failure.
Flame loss after ignition
The boiler established a flame but lost it shortly after — the ionisation probe stopped detecting the flame. Different from A01 (no ignition) because ignition was momentarily successful.
Ferroli boiler fault code table
Extended fault code reference for common Ferroli Modena, DOMIproject, DOMIcompact, and BlueHelix models.
| Code | Meaning | Common cause | Action |
|---|---|---|---|
| A01 | Ignition lockout | No stable flame after multiple attempts | Gas Safe engineer required |
| A02 | Flame loss after ignition | Ionisation probe or intermittent gas valve fault | Gas Safe engineer required |
| A03 | Low water pressure | System pressure below operating threshold | Repressurise to 1.2–1.5 bar (homeowner safe if no leak) |
| A04 | DHW sensor fault | Domestic hot water thermistor failure or wiring fault | Gas Safe engineer required |
| A05 | Gas valve fault | Gas valve not responding correctly to PCB signal | Gas Safe engineer — do not reset repeatedly |
| A06 | Fan / APS fault | Fan motor failure, blocked flue, APS failure | Gas Safe engineer required |
| A07 | PCB fault | PCB internal failure or wiring fault | Gas Safe engineer — PCB replacement likely |
| A08 | NTC sensor fault | Flow or return thermistor failure | Gas Safe engineer required |
| A09 | Flue / overheat sensor fault | Flue gas thermostat or high limit thermostat tripped | Gas Safe engineer — allow to cool first |
| A99 | General PCB lockout | Multiple simultaneous faults or PCB failure | Gas Safe engineer required |
Ferroli boilers in South London hard water areas
Ferroli boilers in South London hard water areas develop limescale faster than higher-spec units — Modena and DOMIproject models in Wandsworth, Lewisham, and Lambeth frequently see A09 and A01 faults on units over 7 years without servicing. Thames Water's calcium-heavy supply accelerates scale build-up on heat exchangers designed to tighter tolerances than premium brands.
Parts availability adds another consideration: some Ferroli components carry a 3–7 day lead time through UK suppliers. On a fault like A06 (fan motor) or A07 (PCB), the wait for parts can make a repair job substantially more disruptive than an equivalent Worcester Bosch or Vaillant repair. Reion factors parts availability into the repair-vs-replace assessment at the diagnostic visit.
Reion recommends annual servicing with a Fernox TF1 or Adey MagnaClean magnetic filter on every Ferroli boiler in South London. Without this, A09 and A01 faults on units over 7 years are predictable.
Ferroli boiler fault code questions
How do I reset a Ferroli boiler after a fault code?
Should I repair or replace a Ferroli boiler showing fault codes?
Why does my Ferroli boiler keep showing fault codes in South London?
Can I fix a Ferroli fault code myself?
How much does a Ferroli boiler repair cost in London?
Ferroli fault code showing on your boiler?
Reion is Gas Safe registered (919881), handles Ferroli repairs, and serves all of South London. Fixed price after the £80 diagnostic — no obligation to proceed, and an honest repair-vs-replace assessment included.
