The wiring in the tailgate was completely destroyed through a short circuit and needs replacement. Basically the washer pipe broke inside the little rubber tube that goes into the tailgate at the top left. The broken pipe must have made its way through the insulation of the wires of the wiring loom causing a short circuit and some wires of the loom burned away.
Does anybody know how to replace the wiring ? The wiring loom just disappears in the top left and I am not sure if it runs all the way under the roof to the fusebox. I am not even sure how this part is called. Searches for "tailgate wiring loom" did not help.

My wiring loom is also damaged, cables are cut, rear wash pipe is cut too. Shame the Grande Punto has such a badly designed wiring loom in that area... I too cannot find any thread about replacing the darn thing. Any suggestions please?