Johnson Starley Quantec HR28CP Fault codes & diagnostics

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

Combi LPG 2015-present
GC Number 47-416-14
Download the Johnson Starley Quantec HR28CP manualThe official installation and service manual (PDF), the document these fault codes were read from. PDF

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Fault codes

All 5 documented codes

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E-01

Your boiler has failed to start up after multiple attempts and has now locked itself out for safety reasons.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Flame rectification sensor
Full explanation for E-01
E03

Your boiler has temporarily shut down because the water inside it has become too hot, which acts as a safety measure to prevent overheating.

High Engineer only £150-350

Parts commonly replaced

  • High limit thermostat
  • NTC thermistor
  • Central heating pump
  • PCB

Related codes

Full explanation for E03
F-15

Your boiler has stopped working because it has been manually reset too many times in a short window, suggesting an underlying fault that needs professional attention.

High Engineer only £120-350

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • Printed Circuit Board (PCB)
Full explanation for F-15
F37

Your boiler has stopped working because the water pressure in the central heating system has dropped too low.

High DIY-safe £0-160

What to check first

  1. Locate the metal braided filling loop underneath or near your boiler.
  2. Slowly open the one or two valves on the loop until you hear water flowing.
  3. Watch the pressure gauge until it reaches between 1.0 and 1.5 bar, then close the valves tightly.

Parts commonly replaced

  • Filling loop
  • Expansion vessel
  • Pressure sensor
Full explanation for F37
F40

Your boiler has detected that the water pressure in the central heating system is too low or too high for it to operate safely.

High DIY-safe £0-160

What to check first

  1. Check the pressure gauge on the front of the boiler or under the casing; it should be between 1.0 and 1.5 bar.
  2. If it is below 1.0, use the external filling loop valves to top up the system until the needle reaches the green zone.
  3. If the pressure is too high, bleed a radiator to release water and lower the pressure.

Parts commonly replaced

  • Filling loop
  • Expansion vessel
  • Pressure sensor
Full explanation for F40
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