Dishwasher, Indesit, Model:DG6100/1?

The heater burnt out, it melted the outer casing of the heater! I have replaced the heater and on testing found that the water fill level is low. My question is: What sort of level control is fitted to this model and where is it located? Also, should there be a T.O.C in the heater cicuit because I can't find one.
I noticed that the colour of connector ends of the heater on the original was blue and on the Meloni replacement they are yellow. Has this any significance?

Frank Shaw
October 2005