Keston 75 Fault Code (Heat 2)

Safety disclaimer

Fault code summary

Manufacturer

Keston

Fault code

75

Fault type

Flue, Fan, Safety lockout

Severity

lockout

Reset

Not specified

Applicable models

Keston Heat 2 45, Keston Heat 2 55, Keston Heat 2 45P, Keston Heat 2 55P

Quick answer

Air-pressure-switch error.

What does this fault code mean?

Air-pressure-switch error.

Common causes

• Air pressure switch error.

Symptoms

• The boiler fault screen shows code 75 and a lockout condition.

What can the homeowner safely check?

• Record the code and do not obstruct or dismantle the flue.

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

• Check the air-pressure safety circuit, fan and flue by a qualified engineer.

Applicable boiler models

• Keston Heat 2 45
• Keston Heat 2 55
• Keston Heat 2 45P
• Keston Heat 2 55P

Related fault codes

• 1 — Heat 2

  Flow thermistor open circuit (blocking).

  Read fault code
• 10 — Heat 2

  Water-pressure sensor defect.

  Read fault code
• 11 — Heat 2

  Flow thermistor open circuit; lockout after 24 hours.

  Read fault code
• 12 — Heat 2

  Flow thermistor short circuit; lockout after 24 hours.

  Read fault code
• 13 — Heat 2

  Return thermistor open circuit; lockout after 24 hours.

  Read fault code
• 14 — Heat 2

  Return thermistor short circuit; lockout after 24 hours.

  Read fault code
• 19 — Heat 2

  Heat thermistor open circuit (blocking).

  Read fault code
• 2 — Heat 2

  Flow thermistor short circuit (blocking).

  Read fault code

Manufacturer documentation

FAULT FINDING MENU (continued): Air Pressure Switch error — code 75.

Last verified

2026-09-12

Frequently asked questions