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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. The EcoTec Plus and Eco Pro 28 boilers are the most likely to display this fault.
You can contact a Gas Safe engineer from BoilerGuide to get your F75 error code fixed.
If you have the manufacturers’ manual to hand from Vaillant, you’ll see that the Vaillant F75 boiler fault code will relate to the following:
Table of Contents
- No pressure change detection when starting boiler pump.
- Faulty Pressure Sensor Causing a Vaillant F75 Error Code
- Faulty Vaillant Boiler Pump Causing a F75 Fault Code
- How to Diagnose the F75 Boiler Fault Code
- How Much Does it Cost to Fix a F75 Fault on a Vaillant Boiler?
- What’s Next? Still need help or have questions about your boilers?
No pressure change detection when starting boiler pump.
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 is going to lie with one of two things:
- The boiler’s pressure sensor.
- The central heating pump.
The diagnostic process of the f75 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 a 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. One of these parts was the pressure sensor inside the boiler.
Since the original EcoTec boiler was launched, there have been three major overhauls of the EcoTecs’ pressure sensor.
The newer boiler models are much stronger and more durable. If you have an EcoTec that is from 2005-2010, it’s likely that it has an older (less reliable) pressure sensor, and there is a good chance it has failed.
But what makes this boiler fault develop?
A big killer of central heating boiler systems is debris. This includes sludge and lime scale. And 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.
Faulty Vaillant Boiler Pump Causing a 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 be that there is a Wilo pump installed, and that is the problem.
How to Diagnose the F75 Boiler Fault Code
Start by Checking the Boiler Pump
The easiest way to diagnose the F75 fault code of the Vaillant boiler is to first start with the pump. If the pump is working correctly, then the problem is going to be 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 a replacement pump will need to be fitted.
Next, Check The Pressure Sensor On Your Boiler
If there’s noise and vibration, the problem is most likely 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 a F75 Fault on a Vaillant Boiler?
Costs of replacing both the pressure sensor and central heating pump on your boiler will vary. The variation in price will come from:
- The cost of parts depending on the type of Vaillant boiler you have
- Ease of the job. Some boilers are much easier to access than others and this reduces labour time (and cost).
Cost to get a new a Boiler Central Heating Pump for your Boiler
Expect to pay: £240-300 to 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?
Or, if you have a boiler fault not listed, leave a comment and we’ll respond as soon as we can.