Vaillant boiler fault codes

Vaillant boiler fault codes

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 or an issue with its operation.

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 is 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)
• Defective electronics

F.62: Fault – Gas valve switch-off delay

• Delayed shutdown of gas valve
• Delayed extinguishing of flame signal
• Gas valve leaking
• Defective electronics

F.63: EEPROM error

Defective electronics

F.64: Electronics/NTC fault

Supply or return NTC short circuited, electronics defective.

F.65: Electronic temperature fault

Electronics overheating due to external influences

F.67: Electronics/flame fault

Implausible flame signal, electronics defective.

F.68: Unstable flame signal fault

This could be caused by:

• Air in gas
• Gas flow pressure too low
• Incorrect 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 the supply line to water pressure sensor or water pressure sensor defective

F.74: Water pressure sensor signal outside the correct range (too low)

Cable to water pressure sensor has short-circuited 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
• Water pressure too low in boiler; check the pressure gauge and repressurise to 1 bar if needed

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 the hot water NTC is not bridged.

F.83: Flow and/or return temperature sensor temperature change fault

• When the burner starts, the temperature change registered at flow and/or return temperature sensor is non-existent 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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