How much does it cost to fix Johnson Starley error code b18?

Typical repair cost for the Johnson Starley b18 fault is £90-180 including labour.

b18 High

Johnson Starley b18 Fault Code

Q: What does the Johnson Starley b18 fault code mean?

Your heater has automatically switched off because the air in the vents has become too hot, usually caused by blocked airflow or a lack of ventilation.

Also written as B18 — same fault.

The Johnson Starley b18 fault code means: your heater has automatically switched off because the air in the vents has become too hot, usually caused by blocked airflow or a lack of ventilation.. It appears on 3 Johnson Starley models in our database.

Technical description: Burner blocked due to high duct temperature

Typical repair cost £90-180 (including labour)

DIY fix possible

Check all heating vents and grilles around the house to ensure they are fully open and not blocked by furniture or curtains.Inspect the air filter on the unit and clean or replace it if it is clogged with dust.Ensure the intake and exhaust terminals outside your property are clear of debris, leaves, or snow.

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Johnson Starley models that show the b18 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Johnson Starley b18 fault code information on this page is sourced and cross-checked against the official Johnson Starley service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026