Vaillant F20 fault error

[Old Account]

hi guys,

As mentioned in the title I am going to visit a customer today and she has got a Vaillant f20 fault code. I would like to pick your brains and ask what it could cause the boiler to overheat?

Don’t get me wrong I know a few reason but perhaps it is a common fault and you could guide me in the right direction to diagnose the right part.
Or you could tell me what could be causing it so I could check few things to determine what exactly the cause is.

Thank you guys for your help in advance.

Kind regards

Ron

 

[Harvest Fields]

Which model of Vaillant is it Ron?

 

[Old Account]

Which model of Vaillant is it Ron?

Vaillant ecotec plus series which model can’t tell 100% haven’t been there yet but she said it’s the 172-082

 

[Old Account]

I also don’t know if she has got a filter installed, or when the last service was, if there is any noise at the boiler. I am sorry I can only get back to you with more details if you require it at 2pm

 

[Harvest Fields]

NTCs? Earth/harnesses/electrodes or harness.

 

[Old Account]

NTCs? Earth/harnesses/electrodes or harness.

Thanks harvest, mice have bitten the harness