vaillant VCW T3 W boiler will not make hot water

[purplehazeuk]

I have an old vaillant vcw t3 w and just recently it has stopped making hot water on demand. the c heating works and when the boiler is alight with the central heating it will make hot water.

I should say that before this problem there were other problems.
sometimes the boiler would make hot water and then stop after a few minutes. this was more during the summer months. also the radiators used to get hot when making hot water even though the ch was switched off.
Also the flow of water through the boiler is quite slow which suggests limescale blocking it the coil ?

This is a great boiler and im reluctant to get rid as i know its a good boiler.

Thanks in advance for your help

Mark

 

[Agile]

It sounds as if the wax element in the diverter valve has failed !

That assumes that the boiler is actually switching on when you run a hot tap.

The flow detection unit underneath operates microswitches in the base of the electronics box.

Tony