Fix the Vaillant F75 Fault Code on Vaillant Boiler: What Causes It?

The F75 fault code is one of the most common Vaillant boiler problems and relates to pressure issues. The EcoTec Plus and Eco Pro 28 boilers are the most likely to display this fault.

In this guide, we’ll walk you through the causes, solutions, and costs to fix the F75 Vaillant boiler fault code. Read on to find out more!

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What Is the F75 Vaillant Boiler Fault Code?

The boiler manual lists the following potential causes of the Vaillant F75 fault:

Water pressure sensor and/or pump defective, air in heating installation, too low pressure in boiler; connect external expansion vessel to return.

The boiler itself could be working correctly, but the F75 fault error code may point to 1 of 2 things:

  1. The boiler’s pressure sensor.
  2. The central heating pump.

The diagnostic process of the F75 Vaillant fault is not particularly easy, and it’s easy to miss other related faults in boilers. So, if in doubt, you’ll need to contact a Gas safe engineer.

Faulty Pressure Sensor Causing the Vaillant F75 Error Code

The Vaillant EcoTec range boiler is constantly being developed. Part of the reason for this is that the earlier boiler models had some very poorly made parts. And, one of these previously faulty parts was the pressure sensor inside the boiler.

Since the original EcoTec boiler was launched, there have been 3 major overhauls of the EcoTecs’ pressure sensor. So, luckily, the newer boiler models are much stronger and more durable. If you have an EcoTec that is from 2005-2010, it likely has an older (less reliable) pressure sensor, and there is a good chance it has failed — which is why you’re getting the F75 on your boiler.

But what makes this boiler fault develop?

Debris is a major killer of central heating boiler systems. This includes sludge and lime scale.

Prevention methods include installing a scale reducer, magnetic system filter installation and ensuring the system is dosed with inhibitor.

It may be (especially if no fault prevention methods are in place) that the sensor on the boiler has become blocked with debris.

Malfunctioning Boiler Pump Causing the F75 Fault Code

One of the most popular manufacturers of central heating boiler pumps today is Grundfos. They are strong, durable, and reasonably priced for all different types of boilers. Manufacturers such as Vaillant and Glow-Worm use them in their boilers as standard.

Unfortunately, the older Vaillant boilers used an inferior pump. The brand, Wilo, has slowly declined in reputation, as their pumps have become known for failing well before they should. If you have an older Vaillant EcoTec boiler, it might have a Wilo pump installed, and that’s what’s causing the problem, and the F75 on your boiler.

How to Diagnose the F75 Vaillant Boiler Fault Code

Start by Checking the Boiler Pump

The easiest way to diagnose the F75 fault code of the Vaillant boiler is to start with the pump. If the pump is working correctly, the problem is likely caused by the pressure sensor.

When a boiler fires, a heating pump will kick into action. This will circulate the water around the pipe-work and central heating.

You’ll recognise the noise as a soft humming noise, and it’s likely you’ll feel the boiler vibrating slightly. If there is no noise or vibration, then the pump is probably not operational, and you’ll need to fit a replacement pump.

Next, Check the Pressure Sensor On Your Boiler

If there’s noise and vibration, the F75 fault most likely concerns the pressure sensor on your boiler. This can be fixed by cleaning out the sludge in the boiler. But the time it costs in labour means it makes more sense to replace the whole pressure sensor for a new one.

How Much Does it Cost to Fix the Vaillant F75 Fault Code?

Costs of replacing both the pressure sensor and central heating pump on your boiler will vary. The variation in price will come from:

  1. The cost of parts depending on the type of Vaillant boiler you have
  2. Ease of the job. Some boilers are much easier to access than others and this reduces labour time (and cost).

What kind of fuel does your boiler use?

Grab your fixed price online by 3PM, and get next-day boiler installation.

Worcester boilers installed from as little as £1,965.

Cost to Get a New a Boiler Central Heating Pump for Your Boiler

Expect to pay £240-300 for a top brand like Grundfos.

Cost to Get a New Boiler Pressure Sensor

Expect to pay £185-240.

What’s next? Still need help or have questions about your boilers?

Got other Vaillant boiler problems? We’ve covered F22, F27, F28 and F29 Vaillant Boiler Faults here and here the vaillant f61 fault code

Ready to upgrade to a new Worcester Bosch boiler? You can get boiler quotes in less than 2-minutes using this clickable form.

Or, if you have a boiler fault that’s not listed, leave a comment and we’ll respond as soon as we can.

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