Ariston · Clas ONE
703 boiler fault code
Clas ONE combi
Get a Gas Safe engineer
Free. Enter your postcode.
What 703 means
Zone 3 send sensor defective.
Gas Safe engineer: Contact a Gas Safe registered engineer to diagnose this fault code.
A boiler fault code alone is not a gas or carbon-monoxide emergency. If you smell gas, a CO alarm sounds, or someone has possible carbon-monoxide symptoms, leave and call 0800 111 999 from outside.
Safe check
Note the code shown on the display and contact a Gas Safe registered engineer.
When to contact an engineer
Contact a Gas Safe registered engineer to diagnose this fault code.
Renting? Report it to your landlord or housing provider first. They are responsible for gas safety and boiler repairs, and the repair should not cost you.
Source and provenance
- Ariston document 420010818500 · Table summarising error codes, optional Heating Zone Modules, printed p. 39
installation and servicing instructions
Official Ariston UK library copy; document 420010818500