My boiler Vaillant Turbo Max Plus 824/7

[knsbuilder]

I have vaillant Turbo Max Plus 824/7 Boiler installed in 2003, in 2006 we change pump so said the engineer and twice the diverter valve been replace. Now devlped new fault which is hot water. It comes on and few second later orange light goes out but the green light keeps flashing. Not enough hot water and because of orange light keeps going out the hot water keeps cutting off. Could anyone tell me what now have gone? Thanks

 

[RusClarke10]

Check the system water pressure as the boiler may be overheating due to low water.

If OK then this sounds like a scaled up domestic plate heat exchanger which would need to be replaced.