Vaillant, lack of hot water and yet another problem

[Jogon]

I've put the tap down low, it's still lukewarm, i've turned the temp of the water up and down and still it remains luke warm, I press the I button and it gives me the S.1.4 which supposedly tells me the hot water system is working, but it's not.

The display shows the water being called up and the temp on the display rises but the hot water is still lukewarm, not sure how that works.

Any ideas?

 

[Billy Bob Bob]

and i am being very tolerant for a change