Vailant Turbomax F28 error code

Hi all

I ihave a Vailant Turbomax with a F28 error code.

If I push the 2 buttons to put it into FSH mode it works and sometimes if I just push reset it works.

The boiler had a service before the issue as I have a boiler service plan with 247.

The enginer who did the service come out and said it needed a new PCB which was fitted and the boiler worked ok when he left, this was on Wednesday. The next morning I woke up and it was off again with the F28 code.

Since then the code has been coming up more often and I only have to reset to get it to work.

He is coming back on Monday to take a look and I remember reading something about a wire that needs changing?.

Any tips I can give him as it was Vailant who sugested to him it was the PCB.

Thanks

Vertical or horizontal flue?

Gas supply issue?

Gas is fine, I have a hob and fire.

Flue is horizontal

Thanks

Yeah, but if the regulator is playing up, wouldn’t necessarily notice it on the smaller appliances. Try lighting hob and run boiler - or has that already happened? Could be the gas valve, condensate trap or pipe blocked, or a few other things. Probably best waiting for your engineer, or get someone who specialises in Vaillant boilers.

Gas hob on or off doesn't seem to make aa differene and boiler works if I put into SF mode and then continues to work for quite a time when it goes into normal mode itself.

Just looking for ideas to pass onto engineer and so I am clear so he can't fob me off.

Thanks

There's a jumper on the board that needs to be set depending on the gas valve...he may be referring to that.