412 Boiler Fault Code: What It Means on Every Brand

The 412 fault code appears on 2 brands — Ariston and Chaffoteaux — and it does not mean the same thing on each. The same two or three characters can signal a pressure problem on one boiler and an ignition fault on another, so identify your brand first and use the table below to jump to the right page.

Up to: Engineer may be needed 2 brands use this code Meaning differs by brand

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 412 means	Severity	DIY?
AAriston	Ariston fault code 412 belongs to the '4' functional group, which covers communication, modem, and room sensor circuits. Full guide →	Engineer may be needed	Some checks
CChaffoteaux	Fault code 412 on a Chaffoteaux boiler indicates that the boiler's control system can no longer detect the ambient room sensor assigned to heating Zone 2. Full guide →	Engineer may be needed	Some checks

412 brand by brand

Ariston 412

Ariston fault code 412 belongs to the '4' functional group, which covers communication, modem, and room sensor circuits. The specific sub-code '12' tells the boiler's control system that the room temperature sensor assigned to heating zone 2 cannot be detected or communicated with. In plain terms, the boiler has lost contact with the zone 2 room sensor and is flagging this as a persistent, non-self-correcting fault that requires attention. It is worth knowing that codes 411 through 416 all follow the same pattern — each one indicates that the room sensor for a particular zone (zones 1 to 6 respectively) is unavailable. If your display shows 411, 413, 414, 415, or 416, the diagnosis and fix are essentially the same as for 412, just applied to the relevant zone's sensor.

Causes, fixes & costs for Ariston 412 → · All Ariston codes

Chaffoteaux 412

Fault code 412 on a Chaffoteaux boiler indicates that the boiler's control system can no longer detect the ambient room sensor assigned to heating Zone 2. Without a valid signal from this sensor, the boiler cannot regulate Zone 2 temperatures correctly and will display the fault to alert you that something needs attention. Code 412 sits within a small family of related sensor faults — codes 411, 412, and 413 — each pointing to a temperature or room sensor anomaly in a different heating zone. Code 411 relates to Zone 1's sensor and code 413 to Zone 3, while 412 is specifically the Zone 2 ambient sensor that the boiler considers absent or out of range.

Causes, fixes & costs for Chaffoteaux 412 → · All Chaffoteaux codes

Frequently asked questions

Is the 412 fault code the same on every boiler?

No. 412 means different things on different brands — see the table above. Always identify your boiler's brand (it is printed on the front casing) before acting on any advice about the code.

Can I fix a 412 fault myself?

On some brands there are safe homeowner checks first — typically system pressure, the condensate pipe in cold weather, and a single reset. Where the code is a simple pressure or reset condition, that may be all it needs. Never open the boiler casing yourself.

Who should I call about a 412 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.