Vaillant Boiler Problems: Common Fault Codes & Troubleshooting

Vaillant Boilers - Installation, Repair & Servicing

In this article, we aim to look at the Vaillant Ecotec fault codes, the common combi-boiler problems and take away any problems and questions you may have.

Like most popular boilers, the Vaillant Boiler problems are often easily diagnosed and troubleshooting comes at a price if you haven’t got a decent guide to talk you through it.

We aim to look at the Vaillant Ecotec fault codes, the common combi-boiler problems and take away any problems and questions you may have.

To start, let’s signify the most common fault codes:

  1. Vaillant F22 Boiler fault
  2. Vaillant F27 Boiler fault
  3. Vaillant F28 & F29 Boiler fault
  4. Vaillant F75 Boiler fault

Vaillant F22 Boiler fault

This Vaillant Ecotec Plus fault code also appears regularly on the Ecotec Pro models, chiefly the Ecotec Pro27. If you have this Vaillant system installed, it may be worth familiarising yourself with the F22 Boiler fault.

This error code will display every time there is a lack of pressure or a lack of water or both.

Essentially, this error code is protecting your asset. It is detecting that the boiler is not firing properly and that there is a lack of water and therefore, turning your boiler on to its “limp” mode – this means that no damage can be done to the parts during this time by continuously firing without any water.

Vaillant F22 Boiler fault solution

Firstly it is integral we work out which element is causing the fault. Is it a lack of pressure, lack of water, or a combination or both?

To diagnose this we highly recommend getting an experienced, Gas Safe Registered, Vaillant boiler repair engineer on site to determine what the cause is.

The first thing an engineer will check for is a leak, as it is most commonly the source of problems in pressure loss faults.

Areas that need checking for leaks can range from radiators to pipework and fittings. Whilst checking radiators, an engineer will also ensure that your radiators are not full of air bubbles.

Another issue that could be causing your F22 fault code is a faulty pump – look out for Wilo pumps which have become renowned for having issues as they age and can be known to leak or seize up which results in pressure problems.

Top tip: a common quick fix (but not a longterm fix) can be to use the filling loop to top up the pressure. However, the problem with this hack is that your boiler will continue to lose pressure from time to time and you still haven’t fixed the issue at the source.

Another issue can arise if the pressure has dipped past the 1.5 bar level that is recommended, a simple top up with the filling loop can actually cause even more damage as you are potentially disrupting the balance of chemicals that make up the inhibitor which protects your boiler. This is why we recommend a Gas Safe Engineer be called the moment you see an F22 Boiler fault.

Vaillant F27 Boiler fault

Another equally as common Vaillant boiler fault is to do with the flame.

A faulty flame could occur due to one of the following 4 reasons

  1. The flame sensor is not working and needs replacing
  2. The gas valve is not working so, therefore, a flame cannot be produced
  3. The PCB is not working, but the flame is
  4. If the boiler is not firing at all, the problem is the boiler’s ignition leads

Vaillant F27 Boiler fault solution

Due to the fact we’re looking at flames and gas, it is integral you have a Gas Safe Engineer called out to inspect your boiler and diagnose the situation with care and safety at the heart of what they are doing.

With most boiler faults including faulty parts, it is often more economical to replace the parts, unless the boiler is particularly old or the issue is to do with the PCB.

Due to the cost of the PCB and the time it takes to install one, a simple fix is not possible, certainly not at a price less than £500.

It is with faults like the F27, where we encourage the asset’s owner to take a look at the boiler’s age and the expected lifespan in order to work out whether now is potentially the best time to invest in a new asset altogether.

Vaillant F28 / F29 Boiler fault

This fault is less commonly seen and if you are seeing either of these fault codes there will probably be one clear issue: you won’t have any hot water or heating supplies.

Luckily, the diagnosis is easy: there’s an issue with your gas supply. You can start the process by checking if any of your other gas appliances are still working.

If they don’t – the first place we’d recommend you start is that your gas main or gas meter is working properly and that you have access to gas.

Vaillant F28/29 Boiler fault solution

Unfortunately, the solution is not simple at all if your other gas appliances are absolutely fine. It could be an issue with the ignition leads, ignition unit, the gas valve operation or the air inlet duct.

Items may require simple adjustments or there could be more severe issues with the part.

Much like the F27 fault code, whenever we are looking at gas it is integral that a qualified Gas Safe Engineer is present to thoroughly and safely check over your boiler and ensure that nobody’s life is at risk.

Vaillant F75 Boiler fault

Another hugely common error code is the F75. Once again, this fault is more likely to appear on the Ecotec plus and Ecotec Pro ranges. The fault is indicative of one of these symptoms:

  1. The water pressure sensor or the water pressure pump has become defective
  2. There is air in the heating installation and radiators/pipework
  3. The pressure in the boiler is too low

Essentially, all of these problems could arise because of one-two faulty parts, either the central heating pump or the pressure sensor (or both)!

Vaillant F75 Boiler fault solution

It is more common for the pump to be causing the problem, due to the Wilo pumps we mentioned earlier. If your Vaillant boiler is potentially quite old, it is more likely to include these Wilo pumps.

However, if your Vaillant boiler is brand new, it will have the Grundfos pumps which are decidedly better quality.

Checking the pump is easy to do. You must start up the heating or run your hot water and you should hear your boiler start to fire up.

If the audible noises from the pump stop after the boiler has fired up, it is most likely to be the pump that is causing problems.

If you continue to hear noises from the pump until the tap is turned off or the heating is turned off, it will not be the pump after all.

In this scenario, it will be the pressure sensor causing the problems. Again, if your boiler is old, it will be due to non-durable parts.

An engineer will be able to either replace the parts for what we would expect to be £300 or less, or if you’re lucky it may be salvageable through cleaning any of the muck and debris that is blocking the pressure sensor.

Vaillant Boiler Problems – In Conclusion

As you may have noted throughout our article we do often recommend you look for qualified engineers in many scenarios and that is because boilers are not easy and there are many dangers to playing about with gas if you don’t know what you’re doing.

If you require assistance get in touch with a Gas Safe Registered engineer here.

If you have another Vaillant fault, drop us a line and we’ll be sure to get back to you.

Related articles

5 Easy AC Maintenance Tips to Avoid Emergency Breakdowns

5 Easy AC Maintenance Tips to Avoid Emergency Breakdowns

If you’re looking to save money and energy, you need to make sure you focus on AC tune up. Here are 5 easy AC maintenance tips anyone can do to avoid emergency breakdowns!

Learn More
Electric Central Heating Boiler vs Gas Boiler: Pros and Cons

Electric Central Heating Boiler vs Gas Boiler: Pros and Cons

What are electric central heating boilers and how do they differ from gas boilers? Are there any drawbacks compared to a gas boiler?

Learn More

Emergency Boiler Repair in Ilford

Just been called to a emergency boiler repair in Ilford. The offending equipment was a Britony water heater which had not been working for 15 days. After following the fault rectification process, the fault was identified as permanent pilot which would not stay alight. The thermo-coupler is the part that performs this function & this […]

Learn More