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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?

MK City Plumbing & Heating is here to assist. We are the number one choice for all your plumbing and heating requirements. Give us a call on 01908 464 075, we are here to help!
MK City Plumbing & Heating are your local Vaillant boiler installers who have a wealth of expertise in installing, servicing and repairing Vaillant boilers. In Milton Keynes and surrounding areas, we are known to be your go-to company for fault finding on Vaillant boilers.

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.

Always contact a qualified professional when your boiler displays a fault code. Attempting to repair it yourself can be dangerous and potentially void the boiler’s warranty.

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

MK City 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 01908 464 075 or browse our site for additional information.

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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 MK City 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 Milton Keynes and all surrounding areas.. It is our aim to offer all our customers an exceptional service from start to finish. Our customers at MK City Plumbing & Heating are paramount to us and this will never change.