Vaillant Turbomax plus 828e working intermittently

[Pajee]

I am hoping someone here can help - have looked through this very helpful forum and couldn't find a similar issue discussed.

I have a Vaillant Turbomax plus 828E which works intermittently for both hot water and heating - it comes on sometimes and at other times it doesn't. From what I can tell it is failing to ignite or rather does not get to the ignition phase. It's been working fine for the last couple of days but no doubt it will stop working again in a day or two - has been behaving like this for the past 3 weeks or so. There are no fault codes that appear on the display when it doesn't work - there is demand when I open the hot water tap(green light comes on) but then it doesn't progress to ignition(yellow light). Checked the pressure and this fine - just above 1 bar.

Have had 2 boiler guys come in who have told me different parts need replacing - first one said gas valve and the second one said fan needs replacing - does anybody have any thoughts or opinions as to what the problem might be - appreciate this might be difficult based on the limited information I have provided - any advise will be much appreciated.

 

[ianmcd]

If it was the fan or the gas valve you would get Fault codes, go into the fault history and see what is there

 

[Pajee]

Thanks for the quick response Ian - can you please guide me how to check the fault history to see if there's anything there ? I have not seen any 'F' codes on the display since the problem first started occurring - will there be anything in the fault history if no 'F' codes have been displayed on the panel ?

 

[ianmcd]

Page 77

https://www.freeboilermanuals.com/assets/pdf/vaillant/thermoCOMPACT.pdf

 

[Pajee]

Thanks again Ian for the link to the boiler manual - I checked the fault history and there is one F.22 and nine F.28 codes in the history - according to the manual there could be a number of causes for the codes, is there a way to narrow down the cause ?

Also in the indication column for fault code F.28 it says "Boiler goes to lock out" - the boiler has not gone into lock out, does this indicate the fault code relates to a previous issue that occurred with the boiler and is it possible to clear the fault code history ?