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Vaillant Boiler Fault & Error Codes

If your vaillant boiler is displaying a code beginning with F then it is signalling that the appliance is experiencing a fault. To help get your boiler up and running again, have a look below at each code and what fault it indicates.

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Simply answer a few multiple choice questions about your existing boiler and we’ll give you a fixed price for a new boiler including all parts and installation[28]

Code Meaning Cause
F.49 eBUS fault Short circuit on the eBUS, eBUS overload or two power supplies with different polarities on the eBUS
F.52 Mass flow sensor connection fault Mass flow sensor not connected/disconnected, plug not connected or incorrectly connected
F.53 Mass flow sensor fault Mass flow sensor faulty, filter below venturi filter cap wet or blocked, gas flow pressure too low
F.54 Gas pressure fault (in combination with F.28/F.29) No or too little gas supply pressure, gas valve closed
F.56 Fault: Mass flow sensor regulation Gas valve defective, cable harness to gas valve defective
F.57 Fault during comfort safety mode Ignition electrode highly corroded
F.61 Fault: Gas valve regulation
  • Short circuit/short to earth in cable harness for the gas valve
  • Gas valve defective (coils shorted to earth)
  • Electronic defective
F.62 Fault: Gas valve switch-off delay
  • Delayed shutdown of gas valve
  • Delayed extinguishing of flame signal
  • Gas valve leaking Electronics defective
F.63 EEPROM error Electronics defective
F.64 Electronics/NTC fault Supply or return NTC short circuited, electronics defective
F.65 Electronic temperature fault Electronics overheating due to external influences, electronics defective
F.67 Electronics/flame fault Implausible flame signal, electronics defective
F.68 Unstable flame signal fault Air in gas, gas flow pressure too low, wrong air ratio, condensate route blocked, wrong gas restrictor, ionisation flow interruption (cables, electrodes), flue gas recirculation, condensate route
F.70 Invalid device specific number (DSN) Spare part case: Display and PCB replaced at same time and DSN not set, wrong or missing output range coding resistor
F.71 Flow NTC fault Flow temperature sensor signalling constant value:
  • Flow temperature sensor incorrectly positioned at supply pipe
  • Flow temperature sensor defective
F.72 Flow/return NTC fault Flow/return NTC temperature difference too great → flow and/or return temperature sensor defective
F.73 Water pressure sensor signal in the wrong range (too low) Interruption/short circuit of water pressure sensor, interruption/short circuit to GND in supply line to water pressure sensor or water pressure sensor defective
F.74 Water pressure sensor signal outside correct range (too low) Cable to water pressure sensor has short-circuitedd at 5V/24 V or internal fault in water pressure sensor
F.75 Fault, no pressure change detection when starting pump Water pressure sensor and/or pump defective, air in heating installation, too low water pressure in boiler; check adjustable bypass, connect external expansion vessel to return
F.76 Overheating protection on primary heat exchanger has responded Cable or cable connections for safety fuse in primary heat exchanger or primary heat exchanger defective
F.77 Flue non-return flap/condensate pump fault No response from flue non-return flap or condensate pump defective
F.78 Interruption to DHW outlet sensor at external controller UK link box is connected, but hot water NTC not bridged
F.83 Flow and/or return temperature sesnsor temperature change fault
  • When the burner starts, the temperature change registered at flow and/or return temperature sensor is non-existant or too small.
  • Not enough water in the boiler
  • Flow and/or return temperature sensor not in correct position at pipe
F.84 Fault: Flow/return temperature sensor difference implausible Flow and return temperature sensors return implausible values
  • Flow and return temperature sensors have been inverted
  • Flow and return temperature sensors have not been correctly fitted
F.85 Fault: Flow and return temperature sensors incorrectly fitted Flow and/or return temperature sensors have been fitted to the same pipe/wrong pipe
F.92 Coding resistor fault The coding resistor on the PCB does not match the entered gas family. Check the resistor, repeat the gas family check and enter the correct gas family.
F.93 Gas group fault Combustion quality outside the permitted range: Wrong gas restrictor, recirculation, wrong gas family, internal pressure measuring point in venturi blocked (do not use lubricant on O-ring in venturi.). Gas family check prematurely terminated.
Communication fault No communication with PCB

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[28] Exclusions apply. See www.help-link.co.uk/fixed-price-quote-faqs/

[79] Online discount is available to domestic gas and LPG customers who receive an online quote for all boiler brands excluding Vokera. Discount will be applied as long as the quoted price is still applicable at the point of sale. Online discounted price is only available for the duration of the 14-day quote validity which starts from the day the quote was given. Offer is not available to Help-Link UK Ltd employees.

Online discount can be applied as follows:
All boiler manufacturer types excluding Vokera are eligible for a 5% discount off the final quoted price. Conventional to combi boiler swaps also qualify for an additional £50 discount after 5% initial discount is applied.

This offer cannot be used in conjunction with any other offers.
Offer available from April 2017. Any boiler quotations before this date will not be eligible for the discount post purchase. Help-Link UK Ltd have the right to withdraw or change the offer at any time.
Online discount is automatically applied when the customer gets a quote using the online quote system at www.help-link.co.uk and as long as the customer meets all the above criteria.