DHW problem on a Vaillant Turbomax 828+

[Jay P]

Hi to all and I'm a new member in need of some advice. I have a problem with the DHW on Vaillant 828 boiler at a family friends house. When the hot tap is run the water runs warm for a while, then goes cold and the boiler shuts down although the DHW display showing the water is up to full working temp. I'm getting hot water out of the main heat exchanger and into the plate to plate but by the time it reaches the DHW pipe out of the boiler it's luke warm, I've already changed the diverter valve a couple of weeks ago and it was fine until it started playing up again at the weekend and I've changed the thermistor tonight.
My thoughts point to a plate to plate heat exchanger fault, can anyone confirm this or is there anything else I need to check?? Any expert advice would be very much appreciated and thanks in advance from a fault finding novice.

 

[Barry98]

You need to increase your post count to ten and access to the gsr private section to discus further am afraid

This plumbing forum will not provide advice to anybody with regards to boiler repairs or any other form of gas plumbing without you first providing us with your Gas Safe Registration number in a thread - for very obvious reasons. If you're not qualified to touch gas, you should stay well clear of trying to!