Is your Vaillant boiler displaying an error/fault code? In this guide we have covered all of the most common codes, their meaning and potential solutions.
Vaillant, a popular UK boiler manufacturer, offers a range of combi, system, and heat-only boilers, each equipped with built-in error codes (also known as fault codes).
These codes are designed to alert you to specific issues with your boiler, often causing a bit of frustration and perhaps a few choice words as you decipher their meaning.
By referring to your Vaillant boiler’s manual, you’ll gain a clearer understanding of what each fault code signifies—or at least what it might indicate, as some codes can have multiple interpretations.
The manual will also provide a list of potential solutions, some of which may be manageable for the DIY enthusiast (or their spouse).
However, it’s important to note that most error code resolutions typically require the expertise of a registered Gas Safe engineer.
While your boiler’s manual should be your primary resource, the following guide offers an overview of the most notable error codes and their features in Vaillant boilers.
Let’s dive in!
Key Points:
• Error Codes: Vaillant boilers display error codes to indicate issues.
• Common Codes: F22 (low water pressure), F27 (false flame detection), F28/F29 (ignition failure), F75 (pressure sensor issue).
• DIY Fix: Some, like F22, can be resolved by topping up water pressure.
• Professional Help: Most other codes require a Gas Safe engineer.
• Maintenance: Regular servicing helps prevent these errors.
PS You can check out Gas Engineer Allen Hart explaining the most common boiler problems and how you can resolve them in the video below:
Common Boiler Error Codes of Combi Vaillant Boilers
Rather than provide a list of every single error code associated with the Vaillant boiler ranges, for simplicity, we’ll be focusing on the most common error/fault codes from the brand.
You will notice that some of the boiler ranges have matching error codes.
You may also notice that different error codes can have the same meaning. Reading a Vaillant error code can at times be as clear as trying to find out what’s happening with your teenage child.
In this particular section, we’ll look at Vaillant’s combi boilers.
The most common error codes of Vaillant system boilers and heat-only boilers can be found in the next sections.
Vaillant ecoTEC Plus Combi Boilers
Fault Code | Description |
F.10 Short circuit: flow sensor | Flow temperature sensor is experiencing a defect or a short-circuit |
F.13 Short circuit: Cylinder sensor | Warm start sensor/cylinder temperature sensor is either not connecting or defective |
F.23 Safety switch-off: Temp. spread too large | Temperature spread is too great and the water circulation is low |
F.22 Safety switch-off: Low water pressure | Water pressure is too low or there is either an insufficient quantity of water in the product or none at all |
F.24 Safety switch-off: Temp. increase too fast | The temperature has increased too quickly |
F.25 Safety switch-off: Flue temp too high | The flue gas temperature is too high |
F.32 Fault: Fan | Fan isn’t connected or is experiencing a defect |
F.64 Fault: Electronics/sensor | There is a defect with the electronics, safety-relevant sensor or cable |
F.67 Fault: Electronics/flame | Flame signal is implausible |
F.73 Fault: Water pres. sensor (signal too weak) | Water pressure sensor is showing that the water pressure inside your boiler is too low |
F.74 Fault: Water pres. sensor (signal too strong) | Water pressure is too high |
F.84 Fault: NTCs temp. difference implausible | Temperature difference isn’t plausible |
Communication fault: | There is a communication fault occurring between your boiler’s PCB (inside the electronics box) and the display. |
Vaillant ecoTEC Pro Combi Boilers
Fault Code | Description |
F.10 Short circuit: flow sensor | Flow temperature sensor is experiencing a defect or a short-circuit |
F.13 Short circuit: Cylinder sensor | Warm start sensor/cylinder temperature sensor is either not connecting or defective |
F.22 Safety switch-off: Low water pressure | Water pressure is too low or there is either an insufficient quantity of water in the product or none at all |
F.23 Safety switch-off: Temp. spread too large | Temperature spread is too great and the water circulation is low |
F.24 Safety switch-off: Temp. increase too fast | The temperature has increased too quickly |
F.25 Safety switch-off: Flue temp too high | The flue gas temperature is too high |
F.32 Fault: Fan | Fan isn’t connected or is experiencing a defect |
F.64 Fault: Electronics/sensor | There is a defect with the electronics, safety-relevant sensor or cable |
F.67 Fault: Electronics/flame | Flame signal is implausible |
F.73 Fault: Water pres. sensor (signal too weak) | Water pressure sensor is showing that the water pressure inside your boiler is too low |
F.74 Fault: Water pres. sensor (signal too strong) | Water pressure is too high |
F.84 Fault: NTCs temp. difference implausible | Temperature difference isn’t plausible |
Communication fault: | There is a communication fault occurring between your boiler’s PCB (inside the electronics box) and the display. |
Vaillant ecoFIT Pure Combi Boilers
Fault Code | Description |
F.10 | Flow temperature sensor fault - Short circuit |
F.22 | Safety switch-off because the water pressure inside the boiler is too low. |
F.28 | Boiler ignition fault, unsuccessful ignition when starting up. |
F.29 | Flame loss fault |
F.49 | eBus fault - voltage is too low |
F.65 | Electronics temperature is too high (fault) |
F.71 | Fault with the flow/return temperature sensor |
F.87 | Fault with electrodes |
F.88 | Fault with the gas valve |
F.89 | Fault with the pump |
Communication | Your boiler’s PCB and user interface are not communicating |
Vaillant ecoTEC Exclusive Green iQ Combi Boilers
Fault Code | Description |
F.10 | Flow sensor has short circuited |
F.11 | Return sensor has short circuited |
F.22 | Safety switch-off because boiler water pressure is too low |
F.32 | Faulty fan |
F.64 | Electronics/sensor fault |
F.68 | Fault - the flame signal is unstable |
F.73 | Water pressure sensor fault |
F.74 | Water pressure sensor fault |
F.90 | Communication fault |
Common Boiler Error Codes of System Vaillant Boilers
Moving on to Vaillant’s system boiler ranges, again, we will not list every single fault code but highlight some of the most common ones.
Again, you may notice that some of Vaillant’s system boiler ranges have matching error codes.
For Vaillant’s heat-only boiler fault codes, skip to the section below.
Vaillant ecoTEC Plus System Boilers
Fault Code | Description |
F.10 Short circuit: flow sensor | Flow temperature sensor is experiencing a defect or a short-circuit |
F.13 Short circuit: Cylinder sensor | Warm start sensor/cylinder temperature sensor is either not connecting or defective |
F.22 Safety switch-off: Low water pressure | Water pressure is too low or there is either an insufficient quantity of water in the product or none at all |
F.23 Safety switch-off: Temp. spread too large | Temperature spread is too great and the water circulation is low |
F.24 Safety switch-off: Temp. increase too fast | The temperature has increased too quickly |
F.25 Safety switch-off: Flue temp too high | The flue gas temperature is too high |
F.32 Fault: Fan | Fan isn’t connected or is experiencing a defect |
F.64 Fault: Electronics/sensor | There is a defect with the electronics, safety-relevant sensor or cable |
F.67 Fault: Electronics/flame | Flame signal is implausible |
F.73 Fault: Water pres. sensor (signal too weak) | Water pressure sensor is showing that the water pressure inside your boiler is too low |
F.74 Fault: Water pres. sensor (signal too strong) | Water pressure is too high |
F.84 Fault: NTCs temp. difference implausible | Temperature difference isn’t plausible |
Communication fault: | There is a communication fault occurring between your boiler’s PCB (inside the electronics box) and the display. |
Vaillant ecoTEC Exclusive Green iQ System Boilers
Fault Code | Description |
F.10 | Flow temperature sensor fault - Short circuit |
F.22 | Safety switch-off because the water pressure inside the boiler is too low. |
F.28 | Boiler ignition fault, unsuccessful ignition when starting up. |
F.29 | Flame loss fault |
F.49 | eBus fault - voltage is too low |
F.65 | Electronics temperature is too high (fault) |
F.71 | Fault with the flow/return temperature sensor |
F.87 | Fault with electrodes |
F.88 | Fault with the gas valve |
F.89 | Fault with the pump |
Communication | Your boiler’s PCB and user interface are not communicating |
Common Boiler Error Codes of Regular Vaillant Boilers
Moving on to Vaillant’s regular boiler ranges, again, we will not list every single fault code but highlight some of the most common ones.
Vaillant ecoTEC Plus Regular Boilers
Fault Code | Description |
F.00 | Flow temperature sensor fault |
F.11 | Return temperature sensor short circuit |
F.29 | Fault - flame loss |
F.61 | Fault with the gas valve control system |
F.85 | Temperature sensor fault |
F.87 | Fault with electrodes |
F.88 | Fault with the gas valve |
Communication | Lack of communication between your boiler’s PCB and user interface display |
Vaillant ecoFIT Pure Regular Boilers
Fault Code | Description |
F.10 | Flow NTC has experienced a short circuit |
F.11 | Return NTC has experienced a short circuit |
F.22 | Safety switch-off due to low water pressure |
F.23 | Safety switch-off because the temperature difference is too significant |
F.24 | Safety switch-off because the temperature is rising too quickly |
F.28 | Boiler ignition unsuccessful, failure during start-up |
F.29 | The boiler failed during option and it has failed to re-ignite |
F.32 | Faulty fan |
F.61 | Fault with gas valve regulation |
F.88 | The gas valve isn’t connected |
F.89 | An incorrect pump has been detected |
Con | Lack of communication with the PCB |
Can I Fix a Vaillant Boiler Error Code DIY?
As mentioned earlier, in most cases, it’s essential to hire a qualified heating engineer to fix a Vaillant boiler fault.
This is because much of the work related to boilers and heating systems is neither safe nor legal for a DIYer to undertake—two very compelling reasons to avoid tackling these projects on your own.
Your Vaillant boiler’s manual will clarify whether any of the suggested solutions are safe for DIY attempts.
For instance, if the issue is low water pressure, topping up the boiler can be a straightforward and safe task for a DIYer—if you can turn on a tap, you should be able to manage this.
However, it’s crucial to ensure that a DIY approach is both appropriate and likely to work. There may be clear signs that a DIY fix isn’t suitable or won’t resolve the issue.
For example, if your boiler’s manual suggests topping up the water pressure but your boiler is leaking, it wouldn’t make sense to attempt this fix, as it wouldn’t address the underlying problem.
In short, when in doubt, it’s always best to hire a professional.
Related heating/energy guides:
Cost of Hiring a Professional to Fix a Vaillant Boiler Fault
How much it would cost to have a heating engineer fix a boiler fault can vary widely.
After all, there are countless potential faults a boiler could experience and the solutions can differ greatly.
On the one hand, an engineer may only need to repressurise your boiler (this might cost around fifty quid).
However, let’s say your boiler’s PCB is broken. In this case, you’d be looking at a bill of somewhere in the region of £360 to £790, and that repressurising suddenly looks a whole lot better.
Whatever the case, heating engineers usually charge between £30 and £60 per hour with labour rates differing across the nation.
Then, depending on the type of work involved, supply costs may also apply.
Since there are countless potential fixes for a wide range of Vaillant boiler faults, we’ve listed some of the more common boiler fixes that may apply below.
Here are the average costs of having a faulty boiler repaired:
Repressuring a boiler - £30 to £60
Fixing a leaking boiler - £100 to £500
Bleeding 5-10 radiators - £30 to £120
Bleeding 10-15 radiators - £60 to £180
Power flushing a heating system - £400 to £800
Replacing a PCB - £360 to £790
Boiler fan replacement - £160 to £490
Heat exchange replacement - £460 to £840
Re-pressurising an expansion vessel - £30 to £60
New boiler expansion vessel installation - £460 to £840
Diverter valve replacement - £110 to £260
Brand new boiler installation - £800 to £2,800 *
*While unlikely, it’s always possible that a boiler could be beyond economical repair and need replacing. If you are particularly concerned about the upfront cost for a new boiler instalment (whether soon or in the future), it’s worth considering purchasing a boiler on finance, including zero-interest options.
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