Main 24 Heat ErP Fault codes & diagnostics

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

Natural Gas 2006-present
GC Number 41-467-26
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All 4 documented codes

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FAN LOCKOUT

Your boiler has temporarily stopped working because it has detected an issue with the internal fan that safely removes exhaust gases.

High Engineer only £150-300

Parts commonly replaced

  • Fan assembly
  • Printed Circuit Board (PCB)

Related codes

IGNITION LOCKOUT

Your boiler has failed to light because it cannot detect a proper gas supply or flame, meaning it has temporarily shut itself down for safety.

High Engineer only £150-350

Parts commonly replaced

  • Gas valve
  • Ignition electrode
  • PCB

Related codes

OVERHEAT LOCKOUT

Your boiler has automatically shut down because the internal water temperature became too high, acting as a crucial safety measure to prevent damage.

High Engineer only £150-300

Parts commonly replaced

  • High limit thermostat
  • NTC thermistor
  • PCB

Related codes

THERMISTOR

Your boiler's temperature sensor is failing, so it cannot accurately read how hot the water is and has safely shut down to prevent overheating.

High Engineer only £90-180

Parts commonly replaced

  • NTC Thermistor
  • Temperature Sensor

Related codes

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