How to fix the F75 fault on a Vaillant boiler

Vaillant boilers are mostly extremely reliable, but even the very best boilers will start to become less efficient with age and things can sometimes go wrong. The F75 fault on a Vaillant boiler is one that often comes up on older ecoTEC models due to some teething issues with the pressure sensor and pump during its initial release in the early to mid-2000s. Poorer quality products were used for these parts which has resulted in some homeowners experiencing the F75 fault on their boiler. 

However, even if your boiler isn’t that specific model, it can still develop a fault with age. So, if unit is more than 7 or 8 years old you will want to take extra care to ensure your system stays in good condition until you’re ready to replace it. In this article we will be exploring what the F75 fault means and how it can be fixed so you can be prepared should you ever face the error code on your boiler. 

What does the F75 fault mean and what can cause it? 

If your boiler is showing the Vaillant F75 error code, it essentially means that the boiler is unable to detect any water pressure and therefore can’t distribute the water around the central heating system or through the pipes. This can be caused by there not being enough water in the boiler, so the pressure is too low to be recognised by the sensor. Or it could be that there is a problem with the pressure sensor itself or a fault with the pump. 

Can you hear a low humming and vibration noise coming from your boiler normally? If so that’s a good thing! It means your pump is working as it should be. If the cause of the F75 fault lies with the pump, then you won’t be able to hear any sounds coming from it.  Whereas if the pump starts making its normal noise at first but then stops and you don’t have hot water, the problem will probably be the pressure sensor. 

One of the most common reasons why you can end up with a faulty pressure sensor is because of old boiler water, limescale, rust, and general debris collecting on it over time. When this happens the sensor can’t effectively detect the pressure from the pump which ultimately leads to the F75 fault code being displayed. 

How to fix an F75 fault on a Vaillant boiler 

The first thing to try if you see the F75 fault on your boiler is increasing the pressure in your boiler by topping up the system with water using your filling loop. Even if the pressure drops again and you get the same error shortly after you can rule out the possibility that there simply wasn’t enough water in the system for the sensor to detect as now you can be certain there was. 

If you reset your boiler, you can follow the above-mentioned steps of listening out for the normal pump sounds as a way of potentially locating the source of the fault. If you cannot hear the pump working as it typically would then this is likely the cause of the error code and you will need to call a Gas Safe engineer to come out and replace the pump. 

Equally, if the boiler pump is working fine and it is the pressure sensor that is the issue you will still require an engineer to resolve this problem. However, you will have two options in dealing with the sensor, the engineer could clean it for you, or they could replace it with a new one. It might sound surprising, but the latter is actually the cheaper route to go down as it requires more labour to clean a sensor and remove all the debris. 

Is there any way to avoid the F75 fault? 

Given that the causes of this fault are mostly down the functionality of some key boiler parts there isn’t a lot you can do to stop the Vaillant F75 fault code from appearing. However, one thing you are able to do is ensure that your boiler is regularly serviced every year. This will give the engineer the opportunity to check that the pump is in good working order and clean any minor debris or limescale build-up that they see on the sensor before it has a chance to get worse and show the fault. Also, it never hurts to check your pressure gauge every once in a while, even if your boiler is working normally. 

Conclusion 

It’s normal to worry when you see an error come up on your boiler, replacing a boiler and even new boiler parts can be expensive. However, at NBS we provide high quality boiler replacement parts at competitive prices. No matter what type of boiler you have we’ve got boiler spares that will be exactly what you need. Explore our online shop to find the part you need or if you’re unsure, get in touch with our friendly team today. Also, check out some of our other guides if you are experiencing issues with other Vaillant boiler fault codes.