In case it helps: on a 2003 156 JTD 115 LHD, I got water in on the passenger side and some time after the fan motor stop working. After having cleaned the water pipe below the wind screen to avoid the same thing happening I took the fan out as explained by dtone to test it outside.
The behavior was quite funny: depending on its orientation it was running or not. So I decided to pen it (clumsy clips holding the plastic around the engine) to discover that because of the water on the passenger side some reached the inside of the fan engine and rusted the ground connection.
Some cleaning and extra wire welding for a better ground, close it with some clips missing and back in position.
It has been now running for the last 7 months...
Hope it helps, Carlos