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Vaillant F27 Fault Code

Welcome to the fault-codes section of this site. The following table or page contains the information required to help repair and diagnose the fault codes being shown on the boiler display. You may be guided through the fault finding sequence or steps, for rectifying your boiler with this fault code. Suggested repair solutions may be provided by a link to a repair page. NB Some fault codes are only applicable to a specific range of boilers only.

F.27 Meaning

According to the installation and servicing instructions manual, “safety switch-off: Flame simulation”.  Also according to other sources, “Incorrect Flame Detection Fault (Flame Detection Even Though The Gas Valve Is Off)”


Cause of F27

According to the installation and servicing instructions manual. there is moisture on the electronics, electronics (flame monitor) defective, gas solenoid valve leaking. According to vaillant the causes are as follows.

  • Damage On The Electrode Or The Ignition Lead
  • Moisture Present On The Electronics
  • Fault On The Spark Generator
  • Fault On The Main PCB
Vaillant PCB X20 Connector
Vaillant PCB X20 Connector

Part Nos

Vaillant Electrode 090709
Vaillant Electrode 090709

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