How to fix F75 Fault on a Vaillant Boiler

Vaillant is known to produce some of the most reliable boilers on the market. Despite this, like any appliance, things can do wrong from time to time. This article explains an F75 fault code on a Vaillant boiler and how you can diagnose the issue.

vaillant f75 fault fix PHS Trades Team

What does an F75 fault mean on a Vaillant boiler?

The F75 code is shown on your boilers display console when there is a problem with the water pressure. As a result, your boiler will typically shut down to protect the boiler from any potential damage and as a safety precaution.

The F75 fault code is typically found on the early Vaillant ecoTEC product range. 

What causes an F75 fault?

There are two common causes of an F.75 fault code, they are:

  1. Faulty or blocked pressure sensor
  2. Faulty circulating pump

Why a faulty pressure sensor causes an F75 fault

The pressure sensor is responsible for measuring the pressure in the hydronics loop of your central heating boiler. If the pressure is too high, the is a risk of leakage. If the pressure is too low, there is a risk the heat exchanger will be damaged.

During their lifetime, a boiler’s mechanical parts collect limescale and debris, including the sensor. If the sensor is blocked, it can’t measure pressure correctly, so the boiler shuts down to prevent the abovementioned risks.

You should never open the boiler case to check the pressure sensor. Instead, you must contact a Gas Safe engineer to investigate the issue for you.

How to check the Pressure Sensor

You are, however, able to check to see if the pressure sensor is failing by running a simple test. First, turn your boiler on; if you can hear the pump working but have no hot water or heating, the pressure sensor is likely the fault. Then, contact a boiler engineer to replace the pressure sensor, which is more cost-efficient than cleaning the sensor manually.

Vaillant pressure sensor

The Circulating Pump

The circulating pump is responsible for moving hot water around your central heating system. The pump pushes water from your boiler to your radiators and hot water cylinder. This constant flow of water is what heats your home.

How to check your circulating pump

  1. Reset your boiler, so the error code clears.
  2. Wait for a few minutes for the system to shut down entirely.
  3. Run the hot water tap, and the circulating pump should begin pushing water to the tap.
  4. If your circulating pump has failed, the boiler won’t start working, and there will be no hot water from the tap.

If you experience a short burst of hot water lasting 15-20 seconds, and your boiler shuts down, you likely have an issue with the pressure sensor.

What to do if you have an F75 fault

Unfortunately, you will not be able to repair a faulty sensor or circulating pump. Instead, you will need to contact a Gas Safe registered engineer to replace the defective part.

Book a Vaillant Boiler Specialist

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How to prevent an F75 Code on a Vaillant boiler

The best way to prevent faults in a boiler is to invest in an annual boiler service. A yearly service will prevent unexpected boiler breakdowns, increase the lifespan of your boiler and ensure your boiler runs efficiently. 

Unfortunately, repairs aren’t cheap, and boilers that overwork are expensive. Worse yet, replacing a boiler can cost between £2000 and £5000. 

During your service, your engineer will clean any limescale build-up and test your central heating system. In addition, the inspection will highlight potential issues and allow you to address them before they become a real problem. 

About the author

Trades Team are experts in Heating, Plumbing and Gas Services. We have 15 years of experience providing expert Boiler Repair and Boiler Servicing to homes and businesses across the Southeast. Learn more about Trades Team.

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