Ferroli A16 Fault Code: Causes, Fixes & Repair Costs
What does the Ferroli A16 fault code mean?
The A16 code on a Ferroli boiler indicates a gas valve fault — specifically, the control board (PCB) has lost communication with the gas valve or detected that it is not opening and closing correctly. Because the boiler cannot manage gas flow safely, it triggers a full lockout and shuts down. As an 'A' code in Ferroli's fault system, A16 requires a manual reset to restart the boiler; it will not clear on its own. This fault appears across several Ferroli ranges including the Modena, Bluehelix, Optimax, and i-Series, though the underlying cause and exact behaviour can vary slightly by model — always cross-reference your user manual.
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
- Faulty or failed gas valve Common
The gas valve itself has developed an internal fault, preventing it from opening or closing on demand. This is the most direct cause of A16 and the component most commonly replaced when the code appears persistently.
- Wiring or connector fault between PCB and gas valve Common
The wiring loom or electrical connectors linking the control board to the gas valve can corrode, loosen, or suffer insulation damage over time. A break or poor connection in this circuit will cause the PCB to report a communication failure, triggering A16 even if the valve itself is still functional.
- PCB (control board) failure Sometimes
If the control board cannot send or receive the correct signals to operate the gas valve, it will raise a lockout fault. PCB failures are less common than wiring or valve issues but should be considered when the wiring checks out and the valve tests healthy.
- Low mains voltage supply Rare
Unusually low voltage from the mains supply can prevent the gas valve solenoid from actuating correctly, causing the boiler to interpret this as a valve fault. This is less common but worth noting if other appliances on the same circuit are also misbehaving.
How to fix it
- Check your gas supply is active DIY safe
Before doing anything else, confirm that your gas supply is working — check whether a gas hob or another gas appliance in the property lights normally. If you have a pre-payment meter, ensure it has credit. If there is no gas supply to the property at all, contact your gas supplier rather than an engineer.
- Attempt a single manual reset DIY safe
Most Ferroli boilers have a reset button on the control panel, often marked with an 'R' symbol. Press and hold it for one to two seconds and allow the boiler to attempt a restart. Watch whether it fires up successfully or immediately returns the A16 code.
- Do not reset the boiler more than two or three times DIY safe
If the fault clears and then returns, you may try a second or third reset, but stop there. Repeatedly forcing a lockout boiler to restart when a genuine gas valve fault is present risks damage to other components such as the heat exchanger. If A16 keeps returning, the boiler needs professional attention.
- Do not attempt to inspect or test the gas valve or wiring yourself Gas Safe engineer
The gas valve is a gas-carrying component. In the UK, only a Gas Safe registered engineer is legally permitted to work on, test, or replace gas valves or the associated wiring and seals. Attempting this yourself is both dangerous and a criminal offence.
- Call a Gas Safe registered engineer to diagnose and repair the fault Gas Safe engineer
An engineer will use a multimeter to test voltage and continuity through the wiring loom between the PCB and the gas valve, and will assess whether the valve solenoid is functioning correctly. Depending on the findings, they will repair the wiring, replace the gas valve, or — if the PCB is at fault — arrange a board replacement.
Parts you may need
- Gas valve (Ferroli compatible) · from £110
- PCB / control board · from £130
- Wiring loom / harness · from £35
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 £150–£380, depending on the underlying cause.
Frequently asked questions
Can I fix the Ferroli A16 fault myself?
The only thing you can safely do yourself is check your gas supply is on and attempt one or two manual resets using the boiler's reset button. Everything beyond that — testing the wiring, inspecting or replacing the gas valve, or working on the PCB — must be carried out by a Gas Safe registered engineer. Working on gas components without Gas Safe registration is illegal in the UK.
How much does it cost to fix a Ferroli A16 fault?
A call-out and diagnostic visit typically costs between £80 and £150. If the gas valve needs replacing, expect to pay roughly £250–£350 all-in for parts and labour. A wiring fault is usually cheaper to fix, often within the diagnostic visit cost or with a modest parts charge on top. In rare cases where the PCB is the culprit, replacement costs are typically £200–£300. If your Ferroli is more than ten years old and facing a bill approaching £300 or more, it's worth getting a new boiler quote for comparison.
Why does my Ferroli keep showing A16 after I reset it?
A16 returning after each reset means the underlying fault has not been resolved. A one-off lockout can sometimes be caused by a temporary voltage dip or a minor communication glitch, which a single reset clears permanently. But if the code keeps coming back — particularly more than twice in a short period — the gas valve, its wiring, or the PCB has a genuine fault that needs a Gas Safe engineer to diagnose and repair. Continuing to reset the boiler without fixing the root cause is not safe and can cause additional component damage.
Is A16 the same fault on all Ferroli models?
A16 consistently relates to a gas valve fault across the main Ferroli ranges sold in the UK, including the Modena, Bluehelix, Optimax, and i-Series. However, the specific valve used and the exact wiring configuration can differ between model generations, which affects parts availability and repair time. If your boiler is an older or discontinued Ferroli model, your engineer may need to source parts from a specialist supplier, which can add to the overall repair time. Always confirm the fault meaning against your specific model's user manual.