Common Boiler Problems

Vaillant

Valliant

BBS Plumbing and Heating, north London are professional Gas Safe Register installers for Vaillant gas boilers and OFTEC registered installers for Vaillant oil-fired boilers. We are also are fully qualified and experienced to service, upgrade and repair all Vaillant boiler types, and carry out repairs to existing hot water and central heating systems.

Combi boilers – ECOtec Plus / Pro and Exclusive

Vaillant Fault Codes

Fault codes have priority over all other displays. If a fault occurs, the display no longer shows the current heating flow temperature. If multiple faults occur at the same time, the display shows the corresponding fault codes for two seconds each in sequence.

F. CodeFault
F.0Interruption to flow NTC (feed temperature sensor) – faulty connection and open circuit.
F.01Interruption to return NTC (feed temperature sensor) – faulty connection and open circuit.
F.10 Flow NTC (feed temperature sensor) – short circuit.
F.11 Return NTC (feed temperature sensor) – short circuit.
F.13 Tank NTC (feed temperature sensor) – short circuit.
F.20Safety temperature switch-off by NTC activated
F.22Dry fire – insufficient water in system – faulty sensor – blocked failed pump.
F.23 Water shortage – temperature difference between flow and return
F.24Water shortage – temperature rise too quick – pump blocked – failed – NYC faults.
F.27Incorrect sensing of flame.
F.28Appliance does not start – ignition or gas supply failure.
F.29 Flame goes out after ignition / during operation – gas supply interrupted / faulty earthing.
F.32Fan speed variation.
F.49eBUS under voltage
F.60Electronic faults.
F.61Gas-valve control defective.
F.62Gas valve shut off delay
F.63EEPROM error.
F.64Electronics / NTC fault.
F.65 Electronics temperature too high.
F.67Flame detector input signal is outside the limits.
F.70No valid DSN in display and/or main board.
F.71Flow NTC reports constant value.
F.72Flow and/or return NTC fault.
F.75No pressure rise detected on pump start up.
F.76Overheating protection on primary heat exchanger triggered.
F.77Condensate pump or feedback of accessories blocks heating.
F.78Wrong configuration.
ComNo communication to the main board.

Please Note: The above error codes all refer to different problems with the boiler and you will need to call an qualified and experienced Gas Safe Potterton service engineer, such as BBS Plumbing and Heating, for further advice.

System boilers – ECOtec System plus

Fault codes have priority over all other displays. If a fault occurs, the display no longer shows the current heating flow temperature. If multiple faults occur at the same time, the display shows the corresponding fault codes for two seconds each in sequence.

F.CodeFault
F.0 Interruption to flow NTC (feed temperature sensor) – faulty connection and open circuit.
F.01 Interruption to return NTC (feed temperature sensor) – faulty connection and open circuit.
F.02Interruption cylinder charging sensor actoSTOR (NTC) only in combination with F.91
F.03Interruption cylinder sensor actoSTOR (NTC) only in combination with F.91
F.10Flow NTC (feed temperature sensor) – short circuit.
F.11Return NTC (feed temperature sensor) – short circuit.
F.12Short circuit at cylinder charging sensor (NTC) only in combination with F.91
F.13Tank NTC (feed temperature sensor) – short circuit.
F.20Safety temperature switch-off by NTC activated
F.22Dry fire – insufficient water in system – faulty sensor – blocked failed pump.
F.23Water shortage – temperature difference between flow and return
F.24 Water shortage – temperature rise too quick – pump blocked – failed – NYC faults.
F.25Safety switch-off: Flue gas temperature too high
F.26Fault: Gas valve without function
F.27Incorrect sensing of flame.
F.28Appliance does not start – ignition or gas supply failure.
F.29 Flame goes out after ignition / during operation – gas supply interrupted – faulty earthing.
F.32Fan speed variation.
F.35Air/flue gas duct fault.
F.42 Coding resistor fault (possible in combination with F.70).
F.49eBUS under voltage.
F.52Mass flow sensor connection fault.
F.53Mass flow sensor fault.
F.54Gas pressure fault (in combination with F.28/F.29).
F.56Fault: Mass flow sensor regulation.
F.57Fault during comfort safety mode.
F.60Electronic faults.
F.61Gas-valve control defective.
F.62Gas valve shut off delay
F.63EEPROM error.
F.64Electronics / NTC fault.
F.65Electronics temperature too high.
F.67Flame detector input signal is outside the limits.
F.68Unstable 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.
F.70Invalid DSN in display and/or main board.
F.71Flow NTC reports constant value.
F.72Flow and/or return NTC fault.
F.73Water pressure sensor signal in the wrong range (too low).
F.74 Water pressure sensor signal outside correct range (too high).
F.75No pressure rise detected on pump start up.
F.76 Overheating protection on primary heat exchanger triggered.
F.77Condensate pump or feedback of accessories blocks heating.
F.78Wrong configuration.
F.83 Flow and/or return temperature sensor temperature change fault.
F.84Fault: Flow/return temperature sensor temperature difference implausible.
F.85Fault: Flow and return temperature sensors incorrectly fitted.
F.92Coding resistor fault.
F.93Gas group fault .
ComNo communication to the main board.

Please Note: The above error codes all refer to different problems with the boiler and you will need to call an qualified and experienced Gas Safe Potterton service engineer, such as BBS Plumbing and Heating, for further advice.

AquaPLUS Gas fired, fan assisted combination boiler

AquaPLUS boilers have an inbuilt advanced multifunction diagnostic display to assist with fault finding in the unlikely event of a boiler malfunction.

  • Normal Mode

Under normal conditions the boiler display will show the boiler flow temperature indicating that the boiler is operating correctly after an internal self check.

  • Fault Mode

Should a fault develop in the boiler the display will show a fault code indicating what the problem may be- see table below:

Display Key
1Fan speed malfunction.
2Heating demand.
3Hot-water demand.
4Power store on (Comfort mode).
5Pump on.
6Gas valve on.
7Actual Heating-system flow temperature OR Displaying of a status/error code.
8Correct burner operation (normal flame) or lock out (crossed-out flame.

Error codes

Fault codes take priority over all other display functions in the event of a system fault occurring.

If multiple faults occur, the corresponding fault codes are displayed alternately for about two seconds each – see table below:

DisplayIndicationCause
F.00Flow-NTC: NTC broken; NTC cable broken; Defective connection at NTC / Defective connection at electronicsFlow-NTC cable defective/broken NTC faulty.
F.01Return NTC: NTC broken; NTC cable broken. Defective connection at NTC / Defective connection at electronicsReturn-NTC cable defective/broken NTC faulty.
F.02DHW-NTC: NTC broken; NTC cable broken; Defective connection at NTC / Defective connection at electronics.DHW- NTC cable defective/ broken NTC faulty.
F.03Tank-NTC: NTC broken; NTC cable broken; Defective connection at NTC / Defective connection at electronics.Tank- NTC cable defective/ broken NTC faulty.
F.10Short circuit – flow-NTC NTC-plug shorted to casing; NTC defective.
F.11Short circuit – flow-NTC NTC-plug shorted to casing; NTC defective.
F.12short circuit DHW- NTCNTC-plug shorted to casing; NTC defective.
F.13short circuit DHW- NTCNTC-plug shorted to casing; NTC defective.
F.20 Over heat cut off activated.Maximum temperature exceeded.
F.22Dry fire protectionNo water in appliance – pump cable defective – pump blocked or defective – pump output too low.
F.23Dry fire protection (difference between flow and return NTC’s too large).No water in appliance – pump cable defective- pump blocked or defective- pump output too low.
F.24 Dry fire protection (temperature gradient of flow NTC too steep).Air in boiler/system – pump blocked or defective – pump output too low.
F.27No demand to gas valve.Electronic board defective; Gas valve defective.
F.28Boiler goes to lock out.No gas; Insufficient gas; Incorrect gas valve adjustment; Electrode defective; Ignition lead defect; Electronic igniter defective.
F.29Flame extinguished re-ignition unsuccessful.Gas supply absent or insufficient.
F.32Main heat exchanger anti freeze protection mode due to fan speed deviation too great.Check fan control cables/connections; Defective fan control cable.
F.33Main heat exchanger anti freeze protection mode due to no switching signal from the air pressure switch.Check air pressure switch/fan/fan supply or flue system.
F.37The rotary speed of the fan is too high or too low.Air pressure switch defect; fan defect; electronics defect
F.41No setting for the type of gas is stored.Set gas type in PCB.
F.42Faulty cable loom.Faulty or incorrect loom fitted.
F.43Faulty cable loom. Faulty or incorrect loom fitted.
F.60Electronic fault.Electronics defect.
F.61Electronic fault.Electronics defect.
F.62Flame rectification present 4 secs. after gas valve turns off.Check gas valve or burner tubes and injectors or electronics defect.
F.63EMC fault.EMC or electronics defect.
F.64 Sensor or electronics fault.Check NTC’s/connections or electronics defect.
F.65PCB processor temperature too high.Check earth connection or electronics defect.
F.66Display fault.Display defect; fault in the connection to the display; electronics defect.
F.67Electronic fault. Electronics defect.

The AquaPLUS boiler can also provide a further two diagnostic code displays:

  • Status Mode – used to diagnose faults where a fault code is not displayed.
  • Diagnostic Mode – to assist with the pinpointing of a particular fault it is possible to use the boiler display in diagnostic mode to interrogate the boiler about the status of certain components.

Please Note: The above error codes all refer to different problems with the boiler and you will need to call an qualified and experienced Gas Safe Potterton service engineer, such as BBS Plumbing and Heating, for further advice.

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