Lay the dishwasher on it's side & take off the bottom tray. Be careful about the flood switch & float attached to the tray. The thermostat is attached to the underside of the wash tub floor. In contact with the stainless steel so it can measure the heat. Have you determined that the fault is caused by the thermostat. No heating can also be a faulty heater, faulty wiring from control board down to heater or a fault with the control board not switching the heater on. Have you tested everything with a multimeter?
Lincoln Appliance NZ
February 2019