hot water cutting out boiler/heating

[jmc29]

i have an old valliant combicompact. as soon as u turn on the hot water tap whilst heating is on the boler cuts out but restarts when u turn the tap off. The hot water is nt heating up and tap runs cold. Can anyone shed some light on what the problem ma be. Thanks

 

[Porque223]

If you post a link to whatever manuals you can find on this one maybe a clue can be found.

 

[matt1e]

Problem with diverter valve/servo control or DHW micro switch
others on here will advise better as to the most likely

Matt

 

[Porque223]

And hopefully the most likely will be the least costly.