Glow-worm F5 Fault Code (Flexicom cx)

Safety disclaimer

Fault code summary

Manufacturer

Glow-worm

Fault code

F5

Fault type

Overheating, Safety lockout

Severity

high

Reset

Not specified

Applicable models

Flexicom cx

Quick answer

Overheat fault.

What does this fault code mean?

Overheat fault.

Common causes

This information was not provided in the verified manufacturer source.

Symptoms

This information was not provided in the verified manufacturer source.

What can the homeowner safely check?

This information was not provided in the verified manufacturer source.

Boiler reset information

Reset information was not provided in the verified manufacturer source. Do not repeatedly reset an unresolved fault.

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

Engineer diagnosis information was not provided in the verified manufacturer source. A qualified engineer should diagnose the appliance safely.

Applicable boiler models

• Flexicom cx

Related fault codes

• F1 — Flexicom cx

  Ignition fault.

  Read fault code
• F22 — Flexicom cx

  Low water pressure or ignition temperature rise too slow.

  Read fault code
• F25 — Flexicom cx

  Circulation fault.

  Read fault code
• F3 — Flexicom cx

  Fan unable to reach ignition speed.

  Read fault code
• F77 — Flexicom cx

  Condensate pump error (optional).

  Read fault code
• F9 — Flexicom cx

  Water pressure sensor fault, blocked flow filter or pump fault.

  Read fault code

Manufacturer documentation

F5 | Overheat Fault

Last verified

2026-09-12

Frequently asked questions