Vaillant ecotec F.75 fault

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I can repair your Vaillant ecotec F.75 problem with one visit. I specialise in Vaillant combi boiler repairs. Please give me a call on 07515058714 to arrange a visit by a local Gas Safe registered Vaillant expert.

The F.75 fault code is a very common problem with the Vaillant ecoTEC models. This issue affects all ecoTEC models including the first version manufactured between 2005 – 2012 and the second version manufactured from 2012 onwards. I repair boilers with this problem almost on a daily basis during busy periods. If you are in my locality then I can probably help.

If you look up the F75 fault code in the manufacturers instructions it actually says “no pressure rise was detected on turning on the pump” then lists a number of possible causes.

On the ecoTEC models there is the inclusion of a pressure sensor. The sensor basically has two jobs. Firstly it detects the static pressure in the system. Secondly it detects a small rise in pressure when the pump runs. Essentially the pressure sensor is a safety device. Before the appliance fires up it wants to know firstly if there is enough water in the system, and secondly if the pump is running to distribute the heat so the appliance will not overheat and work safely. Thats the idea.

There is often a correlation between the F75 fault and the F22 fault code(or lack of). The F22 code will present itself when the appliance does not think there is enough pressure in the system to function based on information from the sensor. This could be due to a blocked or failing sensor. Often when sensors are blocked you actually don’t see the F22 fault code as the sensor thinks there is sufficient pressure, even though the boiler may have no pressure in it at all. So depending on what issues you have with your boiler you may see both of these codes at different times or maybe just one of them.

Older Vaillant boilers such as certain ecoMAX models for example, relied on a simple pressure switch to determine if there was enough water in the boiler to proceed with the ignition process. These were a lot less complicated than the sensors and less prone to failure, although they were too simple to determine if a pump was running.

The good news is that the F75 problem can be fixed and you probably do not need a new boiler! The cause of the F75 fault code can be attributed to a number of things. First and foremost the sensor itself can and does fail(a lot). Secondly the pump can be the main cause of the problem or a party to the sensor. Problems with the expansion vessel, which may seem completely unrelated, can and does contribute to the problem. Installation defects such as water quality issues contribute greatly to this problem. Blockages in the sensor are very common and premature pump failure as a result of poor quality water in the system is also very common.

In a perfect world there wouldn’t be installation defects caused by the installers who fit these boilers. Boilers, pumps and pressure sensors etc would work exactly how they were intended to and therefore we would have less problems. In reality it doesn’t happen like this. Only very small bits of corrosion from the radiators left behind can block the pressure sensor on a new boiler and stop it functioning. This makes the pressure sensor a very big weak point on these boilers.

On top of that, early ecoTEC models were supplied with poor quality pumps manufactured by a company called WILO. These were prone to failure and were a very big cause of this problem on early models. These pumps were upgraded to Grundfos pumps which are of a much better quality and much more reliable. I still come across boilers with the early WILO pumps on a weekly basis. Some of these are still working as they should and have yet to be replaced.

So the F75 issue is impossible to diagnose conclusively without an in depth inspection of the appliance by someone who has experience and knows how to fix the problem. Often component failure is actually a symptom, and replacing the failed component may fix the problem short term. Sometimes the cause for continued component failure has to be determined and resolved as a better long term solution. Fitting a magnetic system filter to the central heating return pipe is an example of something that can help.

The F75 fault code usually starts off as an intermittent fault which can be reset for a period of time until the appliance stops working altogether. This usually gives a customer sufficient time to get the issue resolved. If you ignore it the boiler will stop working completely at some point and eventually you will not be able to reset it.

All of the components I have mentioned (sensor, pump and expansion vessel) can be tested in various ways to determine what needs replacing to fix the problem. No guesswork should be necessary for any “engineer” to offer a resolution to the F75 fault. Replacing parts on boilers based on guesswork is almost always an expensive endeavour for someone.

As an end user your only option is to call someone competent, qualified and Gas Safe registered to fix the problem.

It is important to note that this is NOT intended to help other engineers and it is most definitely NOT intended as a DIY self help guide for homeowners trying to fix their own boilers.

If you are an engineer seeking information on how to fix this problem and this has been helpful in some way then thats great. However this page is for information purposes only and cannot be relied upon by someone attempting to carry out any repair – regardless of their qualifications. Read my disclaimer before attempting to use any information on this website.

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I am based in Wath-upon Dearne, Rotherham, South Yorkshire. I cover the whole of Rotherham and most of South Yorkshire, including Sheffield, Barnsley and Doncaster.

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