Ferroli Optimax HE Plus 31 C Fault codes & diagnostics

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

Combi Natural Gas 2009-2017 Discontinued
GC Number 47-267-44
Download the Ferroli Optimax HE Plus 31 C manualThe official installation and service manual (PDF), the document these fault codes were read from. PDF

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Severity at a glance

Each cell = one fault code. Hover to identify.
1 Emergency 11 High 1 Medium 1 Low
Fault codes

All 14 documented codes

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A06

Your boiler is failing to keep a flame lit after multiple attempts, which means it has shut down to protect itself.

High DIY-safe £100-280

What to check first

  1. Check that your gas emergency control valve is in the 'on' position
  2. Check if other gas appliances in your home, like a hob, are working correctly
  3. Press the 'Reset' button on the boiler control panel once

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • Ionisation Lead

Related codes

Full explanation for A06
A41

Your boiler has stopped working because it cannot communicate with the sensor that monitors water temperature moving through the system.

High Engineer only £90-180

Parts commonly replaced

  • Flow temperature sensor (NTC)
  • Wiring harness
  • Main PCB

Related codes

Full explanation for A41
F07

Your boiler is struggling to clear exhaust fumes properly, which means it has safely shut down to prevent the build-up of dangerous gases.

Emergency Engineer only £150-350

Parts commonly replaced

  • Flue fan
  • Air pressure switch
  • Flue seals

Related codes

Full explanation for F07
F10

Your boiler is struggling to detect the flow of water through the system, which means it has stopped providing heating and hot water to protect itself.

High Engineer only £150-250

Parts commonly replaced

  • Flow sensor
  • Wiring loom

Related codes

Full explanation for F10
F11

Your boiler is unable to read the temperature of the water returning to it, so it has safely shut down to prevent overheating.

High Engineer only £120-220

Parts commonly replaced

  • Return NTC sensor
  • Wiring harness

Related codes

Full explanation for F11
F12

Your boiler is having trouble detecting the temperature of the water used for your taps and shower, so it has stopped providing hot water to prevent overheating.

Medium Engineer only £120-180

Parts commonly replaced

  • DHW NTC thermistor

Related codes

Full explanation for F12
F13

Your boiler has detected a problem with the sensor that monitors the exhaust gas temperature, which prevents it from firing safely.

High Engineer only £120-220

Parts commonly replaced

  • Flue sensor
  • Wiring harness

Related codes

Full explanation for F13
F14

Your boiler is struggling to detect the movement of water inside the system, which is preventing it from safely starting up your heating or hot water.

High Engineer only £150-250

Parts commonly replaced

  • Flow switch
  • DHW flow sensor turbine
  • Wiring harness

Related codes

Full explanation for F14
F15

Your boiler is struggling to clear exhaust gases, so it has safely shut down to prevent any unsafe buildup.

High Engineer only £180-350

Parts commonly replaced

  • Fan assembly
  • Wiring harness
  • Printed Circuit Board

Related codes

Full explanation for F15
F34

Your boiler is receiving an insufficient amount of electricity to operate safely and effectively.

High Engineer only £120-250

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Power supply wiring
  • Fuse

Related codes

Full explanation for F34
F35

Your boiler has detected an issue with the quality of your home's electrical supply, meaning the power entering the unit is inconsistent.

High Engineer only £100-£350

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • External Power Supply Filter

Related codes

Full explanation for F35
F37

Your boiler has stopped working because the water pressure inside your heating system has dropped too low to operate safely.

High DIY-safe £80-150

What to check first

  1. Locate the external filling loop, which is usually a small metal or braided hose located under the boiler.
  2. Open the small valve(s) on the loop to allow mains water to enter the system until the pressure gauge on the front of the boiler reads between 1.0 and 1.5 bar.
  3. Close the valve(s) tightly and check that the error code has cleared.

Parts commonly replaced

  • Pressure relief valve
  • Expansion vessel
  • Pressure sensor
Full explanation for F37
F39

Your boiler is having trouble communicating with the outdoor weather sensor, which means it cannot automatically adjust its temperature based on outside conditions.

Low Engineer only £120-200

Parts commonly replaced

  • External temperature sensor
  • Wiring loom

Related codes

Full explanation for F39
F42

Your boiler is struggling to detect the flow of water through the system, which is preventing it from heating your home or providing hot water.

High Engineer only £150-250

Parts commonly replaced

  • Central heating flow sensor
  • Wiring harness

Related codes

Full explanation for F42