Johnson Starley Aquair S Fault codes & diagnostics

3 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.

Heat Interface Unit Natural Gas 36 kW Discontinued
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Just want the most common Johnson Starley Aquair S faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 3 documented codes

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E01

Your boiler is trying to start but cannot light the flame, so it has shut down to keep your home safe.

High Engineer only £120-250 Shared across the range

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Control board
  • Flame probe

Related codes

Full explanation for E01
E03

Your boiler has detected a communication issue with a sensor that monitors the temperature of the exhaust gases, causing it to shut down for safety reasons.

High Engineer only £150-250 Shared across the range

Parts commonly replaced

  • Flue gas temperature sensor
  • Wiring harness

Related codes

Full explanation for E03
E22

Your boiler's electronic control brain is struggling to process its internal settings, causing it to stop运行 safely to prevent potential incorrect operation.

High Engineer only £250-450 Shared across the range

Parts commonly replaced

  • Main PCB
  • EEPROM chip
Full explanation for E22