Vaillant Boiler Fault Codes

Vaillant Boiler Fault Codes

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.

Need help with your Vaillant Boiler?

Croston Plumbing & Heating is here to assist. We are the number one choice for plumbing services & gas-related work. Give us a call at 01257452879.
We are Vaillant boiler installers who have a wealth of expertise in installing, servicing and repairing Vaillant boilers. Locally, we are known to be your go-to company for helping customer fix Vaillant boiler fault codes and issues.

What are the common 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?

Croston Plumbing & Heating specialist is here to assist. If there is a problem, one of our highly skilled repair technicians will be on hand to figure it out quickly and efficiently.
Whether or not you need a new boiler, our experts can help you with this decision. Get in touch with us today by calling 01257452879 or browse our site for additional information.

Here are some of the signs that you boiler needs replacing:


A sure sign that your boiler is due to be replaced is the kettling, gurgling and banging sounds that you might be hearing from your boiler when you run the hot water tap or turn on the central heating

Strange smells

While carbon monoxide does tend to be odourless, some gas companies do add a scent to help it become easier for you to detect if a leak has occurred. An eggy, sulphur-like smell around your boiler is a sure sign that there is a carbon monoxide leak and you should open all the windows and get out of the house as quickly as possible. Contact the Gas Emergency Services as soon as you can.

Yellow flame

A healthy boiler that’s working well should burn with a blue flame. However, if you’ve noticed a yellow flame on your boiler, this could be a sign of a serious issue such as a carbon monoxide problem. This gas is colourless and odourless and often, a yellow flame is the first sign that there’s a problem so it’s important to keep your eye out for it. If exposure levels are high enough, carbon monoxide can lead to serious illness or even be fatal.

Vaillant Boiler Fault Codes

Increase in energy bills

A boiler that is getting old and is increasingly less and less efficient can cost more money than most people can afford to spare. And, upgrading to a boiler that includes modern smart controls will not only improve efficiency but also give you a greater control over your energy usage and spending.

Frequent breakdown

Are you noticing that your boiler is break downing regularly or you are topping up your water pressure every week?

Reduced efficiency

When it comes to energy efficiency, some boilers are just missing the mark due to age. A boiler that’s rated ‘A’ in terms of efficiency will have an energy efficiency level of at least 90%. On the other hand, a boiler that’s rated ‘G’ will have an efficiency level of around 70%, meaning that for every £1 you spend on your energy bill, you’re losing 30p in wasted energy.

Expensive & difficult to find parts

If you’re having increasing problems with your boiler and you have been told by your boiler engineer that new parts are hard to find, it’s a clear sign that your boiler will probably need to be replaced soon. The older a boiler gets, the less likely it is that parts will be readily available. And if you’re struggling to find an engineer who is experienced with the type of boiler that you have, that’s even more reason to consider replacing it.

Do you Need Boiler Finance?

We know that if your boiler cannot be repaired and a new energy efficient boiler is required, then funds may not be available to cover the replacement. Here at Croston Plumbing & Heating, we offer a range of finance options to help cover the cost of the new boiler and installation.

What areas do we cover?

We offer our range of plumbing and heating services to customers in across the North-West. It is our aim to offer all our customers an exceptional service from start to finish. Our customers at Croston Plumbing & Heating are paramount to us and this will never change.