How much does it cost to fix Johnson Starley error code ER 99?

Typical repair cost for the Johnson Starley ER 99 fault is £280-550 including labour.

ER 99 High

Johnson Starley ER 99 Fault Code

Q: What does the Johnson Starley ER 99 fault code mean?

Your boiler's main internal computer has developed a programming error or is not communicating correctly with the rest of the unit.

Also written as ER99 — same fault.

The Johnson Starley ER 99 fault code means: your boiler's main internal computer has developed a programming error or is not communicating correctly with the rest of the unit.. It appears on 1 Johnson Starley model in our database.

Technical description: PCB configuration fault

Typical repair cost £280-550 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Johnson Starley models that show the ER 99 fault code

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

Warmcair DW Repair: £280-550

Source

Johnson Starley ER 99 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