Vaillant F61 / F.61 Fault Code – Causes and How to Fix

May 1, 2021

The Vaillant F61 fault code indicates a fault with either your Vaillant gas valve, the wiring harness, or the PCB.

The gas valve regulates the flow of gas to the burner and is managed by the PCB, the PCB receives various information from numerous sensors within the boiler and throughout the heating system.

The PCB receives this information and then signals to the gas valve to either increase or decrease the flow of gas to the burner which will then directly increase or decrease the flame produced by the burner and subsequently regulate the temperature of the water flowing from your Vaillant boiler.

An F61 Fault Code on a Vaillant boiler suggests that somewhere in the above sequence something has gone wrong, and the boiler has ‘locked out’, the actual definition from the Vaillant manual is:

F.61 Fault: Fuel valve actuation the gas valve assembly cannot be actuated ▶ Check: Cable harness, plug, gas valve assembly (rinse), PCB.

Vaillant F61 Fault Code: Common Causes

The F61 / F.61 Fault Code is one that most Vaillant ecoTec or Vaillant boilers, in general, will suffer at least once in their lifetime. The gas valve opening and closing, electrical signals sent up and down cables, and exposure to extreme temperature differentials all contribute to component failure due to general wear and tear.

Depending on how many times your Vaillant boiler has developed this fault or, how soon after installation your new Vaillant boiler developed an F61 fault, there are often underlying faults that are usually overlooked.

There is a reason why Vaillant will check the water quality of your heating system on every boiler repair, and it’s not just to try and get out of honouring the warranty as many cynical engineers would have you believe.

The reason is that Vaillant and other well-trained engineers understand that it is impossible to separate your boiler from your heating system, the two work together and if one has a problem the other is affected.

If your heating system has poor quality water, it will likely have a build-up of sludge and carbon deposits throughout the radiators and often boiler components including the pump and heat exchanger will be restricted.

If the waterways within the Vaillant heat exchanger and the associated heating system are restricted the pump struggles to push the water around the system meaning the boiler struggles to dissipate the heat it generates and it begins to ‘cycle’

Cycle or cycling is the term we use to describe the boiler going on and off more frequently than it otherwise would if everything were working correctly.

As the Vaillant boiler cycles on and off the components which control and regulate the ignition sequence, the PCB, the wiring harness, and the gas valve will all work harder and more frequently than they would need to on a well-maintained system, and this will directly contribute to early, and possibly frequent component failures.

So, you can see how even though these parts have no direct contact with the system water, they are directly affected by its quality.

Often the fault is with the PCB, which is expensive enough, but unfortunately, it’s not uncommon for both the PCB and Gas Vale to need replacing.

Fixing the Vaillant boiler F61 Fault

A Vaillant boiler F61 / F.61 fault code will usually reset – for a while but eventually a Gas Safe registered engineer will need to attend to safely diagnose and rectify the fault.

As the Vaillant F61 fault relates to a component failure within your Vaillant boiler you will need to contact an engineer, only Gas Safe registered engineers can carry out boiler repairs.

If this is the second or third time you’ve experienced this fault or your Vaillant boiler is relatively new, we would recommend asking the boiler repair engineer to also carry out an advanced annual boiler service including system water analysis and inhibitor top up if necessary.

At Heatsy we’re proud to be recognised as Vaillant Advance installers, we have a wealth of knowledge servicing, repairing, and installing Vaillant boilers of all ages and models.

From the Vaillant ThermoCompact of the late 80s to the popular Vaillant TurboMax plus of the late 90s to the hugely successful Vaillant ecoTec range of the present day, if you have a Vaillant boiler with a problem, we have the experience and skill needed to repair it.

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