3 Flashing Lights on Diplomat Dishwasher?

I have a E3 problem on my ADP8132 Diplomat Dishwasher. Looking at the manual it says 'The dishwasher is unable to heat the water'. Does anyone have any suggestions before I call an engineer? It washing everything okay just doesn't have hot water and when cycle has finished everything is wet, its not drying anything. Any sugguestions would be appreciated. Thank you