Lack of Hot Water

[MicktheNovice]

Hello folks
I think my thermostat is gubbed.
I have a Vokera Linea 24. When I run the hot tap anywhere in the house the temperature indicator starts to change (as normal) and the gas bursts into action to heat the demand. However, very shortly after this it returns to the pilot level and the tap only delivers very slight temperature change ie not HOT water at all.
As its the summer, the central heating isnt getting used so I assume the rads will heat up if I put the CH on.
Anyone else think this component is in need of replacement or is there a test I can do before calling in the experts?
Thanks in advance

 

[spacethegas]

it sounds like the secondary heat exchanger is blocked on the primary side.

 

[MicktheNovice]

it sounds like the secondary heat exchanger is blocked on the primary side.

And that sounds like I shouldnt mess about with it. (the clue is in my name)

 

[spacethegas]

you would need some skill & ability to tackle this problem (the clue might be in your name).