combi boiler, hot and cold water

[jimbles]

I have a ten year old volkera combi boiler
which works fine as far as the central heating is concerned but the hot water has a nasty habit of turning cold. If I open the tap by half this seems to allow the flow of hot water but if I open it fully the water soon turns cold.
Has anyone got any idea as to what the problem could be? am I looking at a new boiler or is it repairable and at what sort of cost?

 

[Fellacim]

Its a common problem with combi boilers. Shounds like your plate heat exhanger needs replacing or cleaning. Is the boiler a vokera linea?

 

[jimbles]

cheers ,it's a vokera 20-80 rs howmatic to be exact. so it's relatively simple
to put right and not too expensive?

 

[Fellacim]

Howmatic? Do you mean a flowmatic? I dont think these have plates in them. You would need to get a gas engineer to have a look at it to check then sensors and gas pressures

 

[jimbles]

yes it's a flowmatic eyes are as bad as the boiler. thanks I'll get the guy out tomorrow.