608 Boiler Fault Code: What It Means on Every Brand

The 608 fault code appears on 2 boiler brands — Ariston and Chaffoteaux — 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 608 means	Severity	DIY?
AAriston	Fault code 608 indicates that the boiler's fan has started up as normal, but the air pressure switch has failed to close to confirm that the flue is clear and combustion gases are being… Full guide →	Lockout — engineer likely	No
CChaffoteaux	Fault code 608 indicates that your Chaffoteaux boiler's combustion fan has started up as normal, but the air pressure switch — the safety device that must confirm adequate airflow before… Full guide →	Lockout — engineer likely	No

608 brand by brand

Ariston 608

Fault code 608 indicates that the boiler's fan has started up as normal, but the air pressure switch has failed to close to confirm that the flue is clear and combustion gases are being safely expelled. Because the boiler cannot verify safe ventilation, it treats this as a combustion safety issue and locks out to protect the household. In plain terms: the fan is spinning, but the component that checks whether air is actually moving through the system hasn't responded correctly. The boiler will not fire until this is resolved. Related air pressure switch faults on some Ariston models may also appear as codes 6P1 or 6P2, which can point to a similar root cause — particularly a damaged venturi tube causing a small air leak that prevents the switch from operating.

Causes, fixes & costs for Ariston 608 → · All Ariston codes

Chaffoteaux 608

Fault code 608 indicates that your Chaffoteaux boiler's combustion fan has started up as normal, but the air pressure switch — the safety device that must confirm adequate airflow before the boiler can ignite — has not closed (activated) as expected. Without this confirmation signal, the boiler cannot be sure that safe combustion conditions exist, so it shuts down as a precaution. In Chaffoteaux's 600-series fault group, code 607 means the pressure switch tripped unexpectedly before ignition, whereas 608 is the opposite scenario: the fan is running but the switch simply hasn't responded. Codes 6P1 and 6P2, which indicate a delay in the pressure switch contact closing, are also related faults you may encounter on the same Ariston-platform models.

Causes, fixes & costs for Chaffoteaux 608 → · All Chaffoteaux codes

Frequently asked questions

Is the 608 fault code the same on every boiler?

Broadly, yes — on Ariston and Chaffoteaux the 608 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 608 fault myself?

Not usually. On every brand listed, 608 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 608 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.