Zannusi ZX5604SI fridge freezer

Visited the above frost free f/f on Sat.
The customer was complaining that the fridge was warm, freezer ok.
The evaporator was all iced up.
There are two elements connected in parrallel. where the two leads of each elements join there is a small black plactic component, the two components are where each side of the elements meet. the wires are sealed in a resin and the components clip onto the pipework of the evaperator.
? Are the components tocs to stop the elements over heating? if so please tell me they are not one time only.
I have looked up the model number on connections but the fridge seems different. the defrost timer on customers f/f/f/f was on its own but connections show the timer integrated with the compressor starter.
Also connections list two seperate elements where as the f/f I was working on the elements are moulded together by the wiring.
Any help gratfully received.