Patrick Garner
Gas Safe Engineer & Installation Manager
Updated 21st August, 2024
If your Vaillant boiler is displaying an error or fault code, it’s essential to understand the cause and how to fix it. Vaillant boilers are equipped with diagnostic codes that alert you to specific problems. This guide will explore common error codes, their meanings, and whether you can fix the issue yourself or need professional help.
Common Vaillant Boiler Error Codes
Vaillant boilers, whether combi, system, or regular, display error codes to indicate issues with water pressure, ignition, sensors, or internal components. Let’s break down the most common error codes for each type of Vaillant boiler.
Vaillant Combi Boiler Error Codes
These boilers combine heating and hot water systems, making them a popular choice for homes with limited space. Here are some of the most frequent error codes seen on Vaillant combi boilers:
| Error Code | Description | Meaning |
|---|---|---|
| F.10 | Flow sensor short circuit | The flow temperature sensor is defective or has a short circuit. |
| F.22 | Low water pressure | Water pressure is too low or there’s insufficient water in the system. |
| F.24 | Temperature rise too fast | The temperature inside the boiler has increased too quickly, often due to poor circulation. |
| F.28 | Ignition fault | The boiler failed to ignite. Causes can range from gas supply issues to a faulty ignition electrode. |
| F.29 | Flame lost after ignition | The boiler loses its flame after ignition, possibly due to gas supply interruption. |
| F.32 | Fan fault | The fan is defective or disconnected. |
| F.64 | Sensor or electronics fault | A fault has occurred in the electronic components or sensors. |
| F.73 | Water pressure sensor signal too weak | The water pressure sensor is showing a weak signal, indicating low water pressure. |
| F.74 | Water pressure sensor signal too strong | Water pressure is higher than it should be. |
Vaillant System Boiler Error Codes
Vaillant system boilers are designed for homes with higher hot water demands. They have separate storage cylinders but still display many of the same fault codes as combi boilers.
| Error Code | Description | Meaning |
|---|---|---|
| F.10 | Flow sensor short circuit | Similar to combi boilers, this indicates a short circuit in the flow temperature sensor. |
| F.22 | Low water pressure | Insufficient water pressure inside the system. |
| F.24 | Temperature rise too fast | The boiler temperature rises too quickly due to issues like poor water circulation. |
| F.25 | Flue temperature too high | The flue gas temperature is higher than safe operating levels. |
| F.32 | Fan fault | The fan isn’t working properly, affecting the system’s ability to vent exhaust gases. |
| F.73 | Water pressure sensor fault | The sensor isn’t detecting the right water pressure levels. |
| F.84 | Implausible temperature difference | The difference between flow and return temperature is outside the expected range. |
Vaillant Regular Boiler Error Codes
Regular (or heat-only) Vaillant boilers are designed for larger homes with more complex heating systems, including external water tanks and cylinders. Here are the common error codes for these systems:
| Error Code | Description | Meaning |
|---|---|---|
| F.10 | Flow sensor short circuit | The flow temperature sensor has malfunctioned or short-circuited. |
| F.22 | Low water pressure | The boiler’s water pressure is too low, preventing proper circulation. |
| F.29 | Flame loss after ignition | The boiler ignites but loses the flame due to a potential issue with gas supply or airflow. |
| F.61 | Gas valve control system fault | A malfunction in the gas valve control system, which regulates gas flow to the boiler. |
| F.88 | Gas valve not connected | The gas valve is not properly connected or has failed. |
Can You Fix a Vaillant Boiler Error Code Yourself?
Some minor boiler issues can be fixed by homeowners, but many require professional intervention. It’s important to check your boiler’s manual to determine whether DIY fixes are safe or advisable.
DIY Fixes
For some error codes, a quick and easy DIY solution is possible. For example:
- F.22 (Low Water Pressure): In many cases, you can resolve this by topping up your boiler’s water pressure using the filling loop. This is a straightforward task that doesn’t require professional help.
- F.28/F.29 (Ignition Issues): Sometimes, resetting the boiler or checking that your gas supply is uninterrupted can resolve the problem. However, persistent ignition problems should be handled by an engineer.
When to Call a Professional
Most Vaillant error codes require the expertise of a Gas Safe registered engineer. Working with gas appliances without the necessary qualifications is dangerous and illegal. Common issues that need professional attention include:
- F.10, F.32, and F.64 (Sensor or Fan Faults): Faulty sensors or fans need to be repaired or replaced by a qualified engineer.
- F.61/F.88 (Gas Valve Faults): Problems with the gas valve are critical and must be addressed by a professional.
Cost of Hiring a Professional to Fix Vaillant Boiler Faults
The cost of fixing a Vaillant boiler depends on the nature of the fault. Below is an estimated breakdown of typical repair costs:
| Repair Type | Estimated Cost |
|---|---|
| Repressurising the boiler | £30 – £60 |
| Fixing a leaking boiler | £100 – £500 |
| Replacing the PCB (Printed Circuit Board) | £360 – £790 |
| Replacing a fan | £160 – £490 |
| Replacing a heat exchanger | £460 – £840 |
| Repressurising the expansion vessel | £30 – £60 |
| Installing a new expansion vessel | £460 – £840 |
| Diverter valve replacement | £110 – £260 |
Boiler repair costs vary based on factors like your location, the specific fault, and the engineer’s hourly rates (typically £30 to £60 per hour). Labour and supply costs add to the overall expense, and it’s always best to get a quote before proceeding with repairs.
Preventing Future Vaillant Boiler Issues
To avoid frequent boiler faults and error codes, consider scheduling regular maintenance. An annual boiler service by a Gas Safe registered engineer will help identify potential issues before they turn into costly repairs. Preventative maintenance includes:
- Checking and cleaning internal components
- Ensuring adequate water pressure
- Inspecting the flue system
- Verifying that the ignition and flame detection systems are working properly
Regular servicing not only improves boiler efficiency but also extends its lifespan, reducing the likelihood of major faults.
When to Replace Your Vaillant Boiler
Sometimes, the cost of fixing a boiler outweighs the benefits, especially if it’s old or beyond economical repair (BER). Consider replacing your boiler if:
- The repair costs exceed 60% of the price of a new boiler.
- Your boiler is over 10-15 years old and frequently breaks down.
- You face repeated issues with major components, such as the gas valve or PCB.
Modern boilers are much more energy-efficient. Upgrading to an A-rated boiler can save you hundreds of pounds on energy bills annually. Moreover, new boilers come with warranties that cover repairs for up to 10-12 years, offering peace of mind and long-term savings.
Conclusion
Understanding Vaillant boiler error codes can save you time and frustration. While some minor issues like low water pressure can be handled as a DIY task, most faults require professional attention to ensure safety and compliance with regulations. Regular servicing can prevent many of these issues from occurring in the first place, ensuring your boiler runs efficiently year-round.
When in doubt, always consult a Gas Safe engineer, and don’t hesitate to replace your boiler if it’s outdated and costly to maintain. A new, energy-efficient model can lower your energy bills and provide long-term reliability.
For further assistance with boiler repairs or replacements, it’s advisable to get a professional quote and ensure you’re working with trusted engineers.
