Vaillant ecotec F27 fault code

vaillant f61-f62 fault code explained and how to fix

The Vaillant F27 fault typically presents itself when the printed circuit board is failing or has failed completely.

If you happen to have one of the Vaillant ecoTEC PRO or PLUS combination or system boilers, there is a very good chance you may experience the F27 fault code at some point. It is a fairly common problem of these first generation models manufactured between 2005 and 2012. The F27 fault code often happens in conjunction with the F61 or the F62 fault codes.

The good news is that the F27 problem can usually be repaired economically and you probably do not need a new boiler! Repairs for this problem is a service I provide. If you are looking for a boiler repair then please get in touch. I have provided information below for anyone looking to purchase the parts needed to fix this problem.

The F27 fault explained

If you look in the Vaillant installation manual regarding the F27 fault it states the following;

“Safety switch-off: Flame simulation” – “Moisture on the electronics, electronics (flame monitor) defective, gas solenoid valve leaking”

This fault is usually a straight forward repair. However if you are not familiar with the problem and you try to follow the manufacturers instructions then you could find yourself wasting a lot of time and money. 9 times out 10 this fault can be attributed to a faulty printed circuit board. Often it will keep working intermittently and will allow you to reset the boiler for some time, but eventually it stops working altogether.

A lot of the time I get called to fix this fault where others have tried and failed, and I can almost guarantee that at least one of the components they have replaced is the spark electrode assembly which also acts as the ionisation probe. This is a complete waste of time and money.

Vaillant ecoTEC F27 fault

Of all the Vaillant ecoTEC boilers I have repaired over the last six years, I don’t think I have ever had to replace a single spark electrode assembly to fix a problem. Any fault. This includes the F28, F29 and especially the F27 fault.

If you are an engineer reading this for advice on how to fix this problem then you need to make yourself familiar with the process of “flame rectification”. If you understand how flame rectification works then you will understand why replacing this component is an utter waste of waste.

The spark electrode assembly is essentially just a of metal rod. All it needs to be able to do is conduct electricity. Thats it. It is not a sensor, nothing particularly special happens here, it all happens back at the printed circuit board. So the spark electrode assembly needs to be clean, in one piece and needs to be able to conduct electricity.

There needs to be a little gap to create a spark and if all the other criteria are met, then this little metal rod can do its job. So save yourself and your customer some time and money by understanding flame rectification and it will make your job easier.

The problem

For whatever reason the printed circuit board fails for no apparent reason and causes this fault. Now the thing with boiler repairs is that you need to categorically identify which components are faulty and replace only the necessary ones as to avoid wasting time and money.

Vaillant ecoTEC F27 faulty printed circuit board

The solution

So if you just assume the printed circuit board is faulty and replace this component you will probably be right, but there are always this occasions where this is not the problem.

For this reason when attempting to resolve the F27 I would recommend trying to get someone who is familiar with the fault to fix the problem. Given that the printed circuit board for these models of boiler retail at around £190 it makes sense to get someone who is not going to guess and start changing parts.

The cost to repair

I offer a Vaillant repair service to fix this problem. I carry genuine brand new Vaillant printed circuit board’s for service and repair. Any parts fitted come with a 12 month guarantee as you would expect. I can usually fix this problem within one visit.

As an end user experiencing these faults, your only option is to call someone competent and Gas Safe registered to fix the problem. Replacing parts on boilers based on guesswork is almost always an expensive endeavour for someone, either the “engineer” or the customer so it is best to try to and find someone who understands this problem and has experience fixing it.

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Areas where I can repair your Vaillant ecotec F.27 fault

areas that are covered

I am located in Elsecar, Barnsley, South Yorkshire. I cover a large part of South Yorkshire including most of Sheffield, Rotherham and Barnsley. I also cover a small part of Doncaster.


I cover most of Sheffield including central Sheffield, Chapeltown, Ecclesfield, Grenoside, High Green, Oughtibridge, Thurgoland, Wortley, Aston, Aughton, Swallownest, Todwick, Hillsborough and Stannington.


I cover the whole area of Rotherham including central Rotherham, Brinsworth, Catcliffe, Canklow, Masbrough, Treeton, Whiston, Greasbrough, Kimberworth, Thorpe Hesley, Rawmarsh, Wentworth, Bolton-on-Dearne, Goldthorpe, Thurnscoe, Wath-on-Dearne, Mexborough, Swinton, Kilnhurst, Hooton Roberts, Ravenfield, Thrybergh, Bramley, Hellaby, Maltby, Thurcroft, Wickersley and Braithwell.


I cover most of Barnsley including central Barnsley, Birdwell, Stairfoot, Worsborough, Kendray, Ardsley, Athersley, Monk Bretton, Lundwood, Royston, Brierley, Cudworth, Cortonwood, Great Houghton, Shafton, South Hiendley, Brampton, Darfield, Wombwell, Hemingfield, Elsecar, Hoyland, Jump, Barugh Green, Cawthorne, Darton, Dodworth, Gawber, Mapplewell, Pogmoor, Staincross, Wilthorpe, Worsbrough, Thurnscoe and Tankersley.


I cover a small part of Doncaster including central Adwick, Conisborough, Edlington, Warmsworth and Mexborough.