apm 8552?

My machine started to make a horrible burning smell and then packed up, further investigation led me to replace the carbon brushes(GREAT)until 2weeks later the machine started to take the main RCD breaker out.
Machine then taken to a local repair shop and diagnosed with the motor at fault(£325 to replace)Sourced a motor for £84+VAT and replaced myself.
Still no action, further investigation led me to the main PCB and burnt out circuit board.
Re-soldered as required and machine works great apart from lack of water temperature.
I accept that the motor could have possibly taken the PCB out but surely not destroyed the complete unit aswell?Any ideas on why i have no hot water temp????:(what is the hot water pipe for when feeding from a combi boiler as this does'nt request the boiler to activate?
I know these Diplomat units are not reliable but i seem to have the whole lot ie washer,dishwasher and the dreaded apm 6855 parasite of a fridge freezer :(.
Any help would be greatlly appreiciated as its the run up to xmas and i'm sure my child would'nt like WHITEGOODS off santa.