There is a rubber gasket that stops water getting into the roof storage area which, over time, can be torn by the action of raising and lowering the roof. To stop water getting into the roof storage area you can replace the gasket or repair it.
- Duct tape or rubber repair kit
Undo the roof lock handles (as if you were lowering the roof) and push up the front of the roof. This will allow you to open the tonneau cover. Once the torneau cover is open you can gently lower the rear of the roof so it hangs above the roof storage area.
Make sure you examine both sides of the gasket for holes and damage
Place tape or repair patch over any holes
Any water should drain down the gully to the drain hole just behind the seat belt mounting. The start and end point of the gully are marked (with a yellow circle) in the pictures shown.
When you close the tonneau cover it will locate in the top of the gasket and form a waterproof seal.
This technical guide was originally held at http://www.fiatbarchetta.com/btech/tonneau%20seal.html. It was copied to this site in 2021 to ensure its availability and to reformat it into a more modern layout. The original guide was written by Ian Barnett.