A16 Boiler Fault Code: What It Means on Every Brand

The A16 fault code appears on 2 boiler brands — Andrews and Ferroli — and on all of them it points to the same kind of problem. The details still differ by brand (thresholds, sub-codes, reset procedure), so use the table below to jump to the page for your boiler.

Lockout — engineer likely 2 brands use this code

Which brand is your boiler?

The brand is printed on the front casing. Tap your brand for the full causes, fixes and repair costs.

Brand	What A16 means	Severity	DIY?
AAndrews	The A16 fault code indicates a gas valve failure on Andrews boilers built on the Ferroli platform. Full guide →	Lockout — engineer likely	No
FFerroli	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… Full guide →	Lockout — engineer likely	No

A16 brand by brand

Andrews A16

The A16 fault code indicates a gas valve failure on Andrews boilers built on the Ferroli platform. The boiler's control system has detected that the gas valve is not operating correctly — it may not be opening, closing, or responding to electrical signals as expected. Because the gas valve is a critical safety component controlling fuel delivery to the burner, the boiler will lock itself out and refuse to fire until the fault is resolved and a manual reset is performed. Note: A16 is documented across the Ferroli boiler range. Andrews Water Heaters (particularly gas-fired combi and system boilers) shares technical platforms with Ferroli under the BDR Thermea group, so if your boiler displays A16, the information on this page applies. Always cross-reference your specific model's manual if unsure.

Causes, fixes & costs for Andrews A16 → · All Andrews codes

Ferroli A16

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.

Causes, fixes & costs for Ferroli A16 → · All Ferroli codes

Frequently asked questions

Is the A16 fault code the same on every boiler?

Broadly, yes — on Andrews and Ferroli the A16 code points to the same class of fault, and the recommended response is similar. Model-specific details such as sub-codes and reset procedures still vary, so follow the page for your own brand.

Can I fix a A16 fault myself?

Not usually. On every brand listed, A16 points to a fault that needs a suitably registered engineer to diagnose and repair. A single reset to rule out a transient glitch is reasonable; repeated resets are not.

Who should I call about a A16 fault?

For gas boilers, a Gas Safe registered engineer — it is a legal requirement for any work on the appliance. If you smell gas at any point, leave the property and call the National Gas Emergency line on 0800 111 999.

General guidance only — not a substitute for professional advice, and not certified by a registered engineer. Any work on a gas appliance must be carried out by a Gas Safe registered engineer. If you smell gas, call 0800 111 999.