Vaillant Boiler Fault Codes

If you encounter a fault code problem with your Vaillant boiler, your focus is getting this problem resolved as quick as possible to avoid the situation continuing.
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 Boiler Fault Codes

Vaillant Boiler Fault Codes

Vaillant boilers use a system of fault codes to alert users to issues within the boiler. The codes below include a wide range of standard and less frequent problems. Please note that if your boiler displays any of these codes, it is advised that you call a Gas Safe registered engineer to investigate and rectify the issue.

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, gas supply or a blocked condensate pipe.

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.

Are you interested in replacing your boiler and avoiding recurrent Vaillant Boiler Fault Codes and problems?

As a reliable and experienced plumbing and heating service provider, Xbg Plumbing & Heating has a team of dedicated professionals who are committed to consistently providing high-quality services to our clients. 

Don’t let plumbing or heating problems cause stress and inconvenience in your life. Trust the experts at Xbg Plumbing & Heating to provide you with the solutions you need. Contact us today to schedule a consultation or request a quote!

Vaillant Boiler Fault Codes

Does my boiler need to be replaced?

We believe in an transparent and honest approach with all our customers, so will always give you the best advice if your boiler needs replacing. There can be a variety of different reasons that will help identify that your boiler may need replacing. The pilot on your pilot light should burn blue, in the event that’s it’s a different colour, then please call us right away.

Additionally, if you notice strange noises from either the boiler or radiators. You may suddenly hear an increase in noise level, this indicates a problem and needs attention by a qualified gas engineer. Finally, and just as important as the other points, any evidence of any leaks or strange smells coming from your boiler, should be treated as urgent. Please call us 01903 536 502, so we can advise you on the next steps.

Boiler Types Explained

combi boiler installation

Combi boiler

A combination or ‘combi’ boiler is both a high efficiency water heater and a central heating boiler in a single compact unit. Combi boilers heat water directly from the mains when you turn on a tap, so you won’t need a hot water storage cylinder or a cold water storage tank in the roof space.

They are also very cost-effective and energy-efficient as water is heated instantly rather than being heated and then stored in a cylinder. An added benefit is that hot water is delivered at mains pressure, which means that you could get a powerful shower without the need for a separate pump.

system boiler installation

System boiler

System boilers require a cylinder for storing hot water, however the major heating and hot water system components are built into the boiler itself, making it quicker and easier to install. In addition, there is no need for a tank in the loft, so it can be an option in a home with little or no loft space or where the space is earmarked for a conversion.

These boilers are also compatible with solar water heating systems, which deliver environmental benefits as well as lower energy bills.

regular boiler installation

Regular boiler

Regular boilers (sometimes known as traditional, conventional or heat only boilers) are ideally suited to homes that already have a traditional heating and hot water system which is linked to a separate hot water cylinder. These boilers also need a cold water storage tank in the loft to feed the hot water cylinder as well as a tank that maintains the water level of the central heating system.

A regular boiler may be the best option for replacing an existing boiler if the property has an older radiator system, as it might not be able to cope with the higher water pressure that is delivered by system or combi boilers