no hot water?

the vokera linea 28 we have currently has no hot water.the heating works fine though.after asking a friend in the trade to take a look he has told me that the hot water sensor has corroded.can you tell me what part or the part number i am suppost to purchase and where is best to obtain it from or do i have to purchase the whole harness section.after looking on the internet i am unable to find it.