Dishwashers use pressure switches that are similar to those used in washing machines. However, instead of having one switching point, they have multiple levels. For example, a two-position switch may switch at 10cm and 15cm of water, while a three-position switch may trip at 15cm, 25cm and 35cm of water.
The above mentioned signs may or may not indicate a faulty heating element. The reasons for the above noted symptoms might be some thing else. The sure way to confirm a faulty heater is using the ohmmeter. It is a device for checking electrical values like resistance between 2 conductive appliances. To test if an element is working or not a professional connects neutral wires to the related connectors on the element and verify it for a positive reading.