Vaillant got an F75 code? It isn't a winning Wonka bar. Here's what F75 means, and how to fix.
Exploring the juice of the F75 fruit below, we'll go as deep for as long as you can hold your breath for.
But you aren't here because you like Googling boiler fault codes.
F75 dragged you here.
F75 isn't a good thing.
Here's what to do.
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Key Points:
F75 error code indicates a failure to detect pressure change in the boiler.
Common causes include a faulty pump, pressure sensor, or a blockage in the system.
Troubleshooting steps involve checking for leaks, ensuring the pump is working, and verifying system pressure.
It’s recommended to consult a Gas Safe registered engineer to diagnose and fix the issue.
Regular boiler maintenance can help prevent this error from occurring.
Fixing the F75 Error Code
Before we begin, it’s important to investigate the cause of the fault code before you become tempted to ignore it and restart your boiler instead.
We understand this temptation, especially in the cold of winter, but this is unlikely to fix the root of the problem. Plus, it’s important to remember why the boiler has “locked out” to begin with:
To protect the boiler from damage.
To safeguard anyone within the property.
It’s also important not to tamper with the boiler yourself, no matter how tempted you might be, opening the boiler casing can be dangerous and should only ever be left to a registered Gas Safe engineer to handle.
What Causes the F75 Error Code?
Pressure!
The Vaillant F75 error/fault code is displayed on the following Vaillant boiler models:
Vaillant EcoPro
The F75 error code is displayed when the boiler is experiencing a pressure issue, resulting in the boiler shutting down or “locking out” and displaying the F75 code via the user interface.
Vaillant officially defines the code as no sudden change in pressure was detected on turning on the pump.
Unlike many other error codes, the F75 error can be the result of multiple boiler malfunctions and so the diagnostic process can be complex.
However, two common potential reasons for the fault are listed as follows:
A water pressure sensor or/and pump defective
Too little water in the appliance; check adjustable by-pass
Faulty Pressure Sensor Causing the Vaillant F75 Error Code
In the early days of the Vaillant EcoTec range, there were some key components that seemed to experience issues more often than others.
Unfortunately, one of these parts was the pressure sensor, which detects pressure changes.
Important note: This common fault was restricted to the early launch of the EcoTec, which ran from 2005 to 2010.
There has been a series of improvements made since then and the issue is not as frequent in newer models.
What else can cause a faulty pressure sensor?
If you have a newer EcoTec pro and don’t suspect it’s related to the manufacturing fault present in some older versions, there are other plausible causes for a faulty pressure sensor.
One of the main causes of a malfunctioning sensor is the build-up of debris on the sensor itself.
For instance, over time dirty boiler water containing the likes of rust, sludge and limescale deposits can leave their mark on your system.
It’s for this reason that Heatable offer a complete system cleanse using a pro flush when we install any new boiler.
We also offer extras, such as inhibitors, for those individuals who reside in hard water areas that are susceptible to limescale deposits.
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Faulty Boiler Pump Causing the Vaillant F75 Error Code
In many modern boilers, including modern Vaillant boilers, a boiler pump by Grundfos is used.
These are some of the most reputable boiler pumps available, renowned for being competitively priced and durable.
Sadly, old Vaillant boilers used to use a less reputable boiler pump, primarily one called Wilo, which over the years has lost favour, becoming known for failing prematurely and experiencing issues.
Therefore, if you have an older Vaillant EcoTec boiler that’s built with a Wilo pump that’s experiencing issues and causing the F75 fault code.
Is your Vaillant boiler experiencing some of the brand's most common fault codes? We have you covered in our F29 fault code and F62 fault code guides.
How to Diagnose the Vaillant F75 Fault Code
As mentioned already, the Vaillant models that seem to be prone to the F75 fault code error are the EcoTEC Plus and the EcoPro 28.
With that in mind, here are a few tips on how to diagnose the root of the problem with your particular boiler:
How to Diagnose a Faulty Boiler Pump
To determine if your boiler's pump is faulty and triggering the display of the F75 error, you can follow these simple steps:
Firstly, reset your boiler by pressing the reset button, this is easy to find as it has a flame icon embossed on it.
Allow your boiler time to restart, this should take a few minutes.
Next, run a nearby hot tap and allow the boiler to fire up and the heat pump to kick in.
Shortly, you should be able to hear the pump operating, which will provide an audible humming sound and gentle vibration.
If the pump is not functioning as normal you probably won't hear or feel anything, signalling that the pump is indeed broken and in need of repair.
However, if your pump is operating as normal but soon falls silent and you lose hot water, the F75 fault is more likely to be the result of a broken pressure sensor.
How to Diagnose a Faulty Pressure Sensor
If your boiler's pump sounded and felt like it was operating as normal, but you still lost hot water and were presented with the F75 error code, then the next most likely cause of the fault is an issue with the pressure sensor.
Pressure sensors in boilers are prone to collecting debris and dirt from the circulating water in your central heating system.
This debris can build up to the point where it will block the pressure sensor from detecting the necessary signals e.g. changes in pressure, resulting in your pump not being triggered and the boiler malfunctioning.
Logically, it may sound like the best option is to clean the pressure sensor and that should do the trick, however, it's usually advised that the part be completely replaced instead.
The usual reason for this is that it makes sense from a financial perspective. Since cleaning can be laborious, it can cost a substantial time in labour costs.
If the sensor itself is in complete disrepair, it may simply mean withholding the inevitable and wasting more money in the process.
Replacement pressure sensors are relatively cheap too.
How to Fix the F75 Error
Unfortunately, there is no DIY fix for the F75 error. If the pump is broken, it will need to be replaced with a new one by a registered Gas Safe engineer.
If the issue lies with a faulty pressure sensor e.g. one that is in need of a cleaning, this will also require the assistance of a Gas Safe engineer.
However, as mentioned, cleaning is rarely advised due to the high labour costs in comparison to the relatively cheap cost of replacing it with a new pressure sensor instead.
Is your Vaillant boiler experiencing some of the brand's most common fault codes? We have covered many Vaillant boiler error codes in the following guides:
How Much Does it Cost to Repair an F75 Error?
If your boiler is displaying the F75 and it is caused by either a faulty boiler pump or pressure sensor, it will need to be diagnosed and repaired by a registered Gas Safe engineer.
The costs will depend on factors, such as the Vaillant boiler model you have e.g. some boilers are more complex and take longer to repair, so naturally cost more to repair as the labour and time required will be greater.
How Much Does a New Boiler Pump Cost?
Excluding installation costs, a replacement boiler pump from a leading brand can cost between £250 and £350 on average.
How Much Does a New Pressure Sensor Cost?
A replacement pressure sensor can cost between £150 and £250 excluding labour costs.
How Can You Avoid the F75 Error?
It's always recommended that you have your boiler serviced annually, in fact, most boiler manufacturers outline that this is a condition of cover.
During the service, the Gas Safe engineer will look for any issues and carry out basic maintenance, including basic cleaning, which will help to avoid parts like the pressure sensor becoming blocked and malfunctioning.
In addition, a routine power flush is advised in order to keep your heating water free from dirt and sludge, a major culprit of blockages and corrosion in your boiler and central heating system.
Unfortunately, sometimes boilers just malfunction, this is especially true of old boilers that are no longer in their warranty period.
If this sounds like you, it may be time to replace your boiler before it starts to cost you more and more in repair costs.
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