Ariston 305 Fault Code (Cares ONE NG)

Safety disclaimer

Fault code summary

Manufacturer

Ariston

Fault code

305

Fault type

PCB/electronics

Severity

lockout

Reset

The manual limits operation-shutdown resets to five in 15 minutes; repeated faults require a qualified technician.

Applicable models

Ariston Cares ONE NG

Quick answer

PCB error.

What does this fault code mean?

PCB error.

Common causes

• PCB error.

Symptoms

• The display shows the 305 operation-shutdown code.

What can the homeowner safely check?

• Record the code and contact a qualified technician.

Boiler reset information

The manual limits operation-shutdown resets to five in 15 minutes; repeated faults require a qualified technician.

When should I call an engineer?

Contact a suitably qualified heating engineer when the fault persists, the boiler locks out, or the manufacturer instructions do not resolve it. For gas appliance work in the UK, use a Gas Safe registered engineer.

Engineer diagnosis

• Investigate the PCB and its connections.

Applicable boiler models

• Ariston Cares ONE NG

Related fault codes

• 101 — Cares ONE NG

  Overheating.

  Read fault code
• 103 — Cares ONE NG

  Insufficient circulation.

  Read fault code
• 104 — Cares ONE NG

  Insufficient circulation.

  Read fault code
• 105 — Cares ONE NG

  Insufficient circulation.

  Read fault code
• 106 — Cares ONE NG

  Insufficient circulation.

  Read fault code
• 107 — Cares ONE NG

  Insufficient circulation.

  Read fault code
• 108 — Cares ONE NG

  Insufficient water; filling is requested.

  Read fault code
• 307 — Cares ONE NG

  PCB error.

  Read fault code

Manufacturer documentation

Operation shutdown error table: P.C.B. error — 3 05, 3 06, 3 07.

Last verified

2026-09-12

Frequently asked questions