01925 357398

At Boiler Repair Warrington we find the most common fault code on Vaillant boilers is F75, while the most common fault code on Glowworm boilers is the F9/F75 code. The Vaillant boilers in question can include EcoTec Plus, EcoTec Pro, EcoMax, and EcoFit, and the Glowworm boilers in the discussion are the CXI, SXI, Felxicom, Energy, and Betacom.

If you receive either of these fault codes, don’t panic — they’re typically easy to fix. However, while they’re simple to fix, they can quickly become a costly repair, especially if your engineer is guessing at what he’s doing rather than following the correct procedures and fault diagnosis process.


What Does the F9/F75 Fault Code Mean?


The F9/F75 fault code means that when your boiler ran its start-up tests and it did not experience a rise in system pressure when the boiler tried to spin the pump. Put differently, according to the official Vaillant boiler manual, “the error message is basically saying that the boiler is not detecting any pressure and is unable to circulate water around the pipes or through the central heating system.”

What Can Cause an F9/F75 Fault Code?

The F9/F75 fault code covers a wide range of issues with your boiler. It’s challenging to pinpoint the exact problem when an engineer first attends to the boiler, which can increase the cost of the repairs. However, there are seven main reasons you might receive this fault code. You might also have more than one of these issues occurring at one time.

  1. Lack of Regular Servicing

Boilers, like any other equipment or appliance, need regular servicing. You can eliminate fault codes by having your boiler serviced at regular intervals by a qualified professional or engineer. You can’t hire just any engineer you come across — you need someone who is specifically trained in how these types of boilers function and run.

Experienced engineers will run your boiler through a gamut of tests to check every vital process and see whether any of them are not running efficiently or correctly. The engineer should also fix any issues they find before further problems pop up.

  1. Blocked Water Pressure Sensors

Another issue you might have, especially if you don’t have your boiler regularly serviced, is a blocked or partially blocked water pressure sensor. Without a functioning water pressure sensor, your boiler cannot tell when there is an increase in pressure while the pump spins. After several attempts to raise the pressure (regardless of whether it is happening or not), the boiler will lockout, and you will get an F9/F75 fault code.

If you determine that a blocked sensor is a problem, you can flush out the area or system to allow the sensor to see rising pressure again. If you install a new sensor, you should make sure it is unobstructed and have the boiler serviced going forward to prevent the issue from happening again. It would help if you made sure that any debris in the system does not block or partially block the water pressure sensor and that it does not damage any other components of the boiler.

  1. Leak

Your water pressure sensor might also be affected by a leak in the system. If you have a leak, the pressure will drop, and the sensor, if working, should read the disruption and give you an F22 fault code. However, if the water pressure sensor is blocked, the pressure gauge will remain at an incorrect reading.

When the boiler spins the pump, the sensor should read a pressure increase of at least 0.2 Bar. If the pressure you’re reading is significantly above the true pressure in the boiler, the pump cannot create an adequate pressure uplift to activate the water pressure sensor. You’ll wind up with an F9/F75 fault code.

  1. Pump Failure

Occasionally you might have a full-scale pump failure on your hands. When if the pump is running slowly or the power supply is disrupted or faulty, you’ll get an F9/F75 code on display. If your pump fails, you will have to purchase and install a new pump.

If you have a Vaillant boiler that was installed after 2012, you need to remove the pump head and replace it. If you have an EcoTec boiler older than 2012, you might need to replace the entire hydroblock component where the pump head connects. Check the boiler or pumps data plate for more information on what you need to replace during pump failure.

  1. Depletion

You might receive an F9/F75 fault code because of an expansion vessel depletion event. The expansion vessel is in a sealed system that is a vital component of the boiler. The vessel must be adequately charged and sized for your system. Expansion vessel depletion is one of the most common issues in a Vaillant and Glowworm boiler, causing an F9/F75 code.

Depletion can happen when the charge of air is too low or high. This affects the amount of positive pressure that the pump can spin, and the pressure sensor can detect. Regular servicing can predict, prevent, and fix expansion vessel depletion.

  1. Blocked Pipework or Heat Exchanger

A blocked pipework or heat exchanger is a less common issue in Vaillant and Glowworm boilers. Unfortunately, many engineers misdiagnose fault codes with blocked pipework or heat exchanger, which can cost customers significant money in unnecessary repairs. Blocked pipework or a blocked heat exchanger is more common in older EcoTec boilers from before 2010, but it is still a less common fault.

Older EcoTec boilers were manufactured with a rubber hose in the flow and return pipes, and the rubber can cause magnetite to build faster than copper pipework. A buildup of magnetite can prevent water from flowing through. You should find out whether your boiler has rubber pipework and exchange the rubber for copper.

The heat exchanger can also become blocked, causing the F9/F75 fault code. However, with the heat exchanger, you typically have warning signs that the system is contaminated. The water pressure sensor will show blockage before the heat exchanger is a serious issue. If the heat exchanger is entirely blocked, it will cost less to buy a new boiler than to replace the heat exchanger.

  1. Faulty PCB

A faulty PCB is extremely rare, and you are much more likely to have any of the other issues before you experience a faulty PCB. The PCB becomes defective when it fails to send 230v of power to the pump. The pump can no longer spin, and after three attempts to start, the boiler will lockout, and you’ll have an F9/F75 fault code.

In most circumstances, if the pump is not spinning, it is usually only seized.

Boiler Repair Warrington

Dallam Court, Dallam Ln, Warrington WA2 7LT

Phone: 01925357398