indesit dl620uk not heating?

Have an indesit dl620uk which is not heating. the water. Have checked the element and the impedence is as expected. the lower thermostat also seems to have continuity when cold. Mt question is, is there another thermostat in the door panel. I have removed the cover and see a control board with a small sensor in a white housing. is this a termostat or just a sensor. how do i test it?