Vaillant Boiler Fault Codes

Vaillant Group is one of the leading heating, cooling, and hot water product manufacturers globally, renowned for their reliable and energy-efficient solutions.

Founded in 1874 in Germany, Vaillant has pioneered numerous innovations in the heating industry, from the first wall-hung boiler to the eco-friendly renewable technologies of today. Vaillant’s commitment to quality, reliability, and customer service has made it a favourite among homeowners.

Vaillant boilers are engineered with advanced technology, and like any sophisticated device, they can present fault codes when something isn’t operating as expected. Understanding these codes can save time and money by helping you diagnose minor issues and know when to call a professional.

Vaillant Fault Codes

• F.00 – NTC Faults: Faults with the NTC thermistor, which provides temperature readings to the boiler’s control system.
• F.10, F.11, F.12, F.13, F.14 – Ignition Problems: Failure to ignite. This could be due to a problem with the boiler’s ignition.
• F.20 – Safety Switch Off: Low-Water Content: The boiler has shut off due to low water pressure.
• F.22 – Dry Fire, Low Water Pressure: The boiler pressure is too low and needs to be repressurised.
• F.23 – Safety Switch Off: Temperature Limiter: The boiler has become too hot.
• F.24, F.37 – Fault: Water Shortage: The boiler has detected a lack of water in the system.
• F.27 – Mains Undervoltage: An issue with the voltage supply.
• F.28, F.29 – Failure During Start-Up: Ignition Fault: The boiler has failed to ignite.
• F.32 – Fan Speed Variance: Fan Running Too Slow: The boiler’s fan is running too slow.
• F.49 – eBUS Under Voltage: This indicates a fault with the power supply.
• F.61, F.62, F.63, F.64, F.65 – Electronic Faults: These indicate various electronic faults within the boiler.
• F.67 – Fluctuation in Mains Voltage: The mains electrical supply to the boiler is fluctuating.
• F.70 – Unrecognisable Configuration: This suggests that there’s an issue with the configuration of the boiler’s settings.
• F.71 – Flow NTC Open Circuit: There is a problem with the NTC sensor in the boiler.
• F.72 – Flow/Water Pressure: The boiler is experiencing water pressure issues.
• F.74 – Flow and Return Sensors: The flow and return sensors are reporting different readings.
• F.75 – Pump or Water Shortage: The pump isn’t working correctly or there’s a lack of water in the system.
• F.76 – Overheating Boiler, Heat Exchanger: The boiler or heat exchanger is overheating.
• F.77 – Flue or Heat Exchanger Overheating: The flue or heat exchanger is overheating.
• F.78 – Flue or Return Sensor Contact: There’s a problem with the contact between the flue and the return sensor.
• F.83 – Fault in Electronic Main Control: There’s an issue with the electronic main control of the boiler.
• F.84 – Flow Sensor Contact Fault: The flow sensor has a contact fault.
• F.85 – Flow Sensor Fault: The flow sensor is not working correctly.
• F.86 – Return Sensor Fault: The return sensor is not working correctly.
• F.92 – Coding Resistor Fault: The coding resistor has a fault.
• F.93 – Incorrect Configuration Coding: The configuration coding of the boiler is incorrect.
• F.94 – Configuration Fault: Gas Family: The boiler’s gas family configuration is incorrect.
• F.95 – Configuration Fault: Gas Type: The boiler’s gas type configuration is incorrect.
• F.96 – Configuration Fault: Gas Controller: There’s an issue with the configuration of the boiler’s gas controller.
• F.97 – Configuration Fault: Gas Quality: The boiler’s gas quality configuration is incorrect.
• F.98 – Configuration Fault: Flue Gas Configuration: There’s an issue with the configuration of the boiler’s flue gas.
• F.99 – System Fault: External: There’s an external system fault.
• F.A1 – Pump Stuck or Running with Water Shortage: The pump is either stuck or running without enough water.
• F.A2 – Pump Overloaded: The pump is overloaded.
• F.A3 – Hot Water NTC Open Circuit: There’s an open circuit in the hot water NTC.
• F.A4 – Hot Water NTC Short Circuit: There’s a short circuit in the hot water NTC.
• F.A5 – Tank NTC Open Circuit: There’s an open circuit in the tank NTC.
• F.A6 – Tank NTC Short Circuit: There’s a short circuit in the tank NTC.
• F.A7 – Hot Water NTC Sensor Fault: There’s a fault with the hot water NTC sensor.
• F.A8 – Break in Communication with IDM: There’s been a break in communication with the IDM.
• F.A9 – Tank or No Hot Water: There’s either an issue with the tank or no hot water.
• F.C0 – Unconfigured PCB: The PCB has not been configured properly.
• F.C1 – PCB Error: There’s an error with the PCB.
• F.C7 – Incorrect Flame: The boiler has detected an incorrect flame.
• F.d.0, F.d.1, F.d.8 – Service Functions: These codes relate to service functions of the boiler.