Clogged sunroof drains can allow water to enter the interior and accumulate under the carpet where various control modules are mounted. Over time, the accumulated moisture can damage the control modules.Google+
Car Problem Reports
Volkswagen Passat TDI Water From Clogged Sun Roof Drains May Damage Control Modules
Volkswagen Passat TDI Problem
Visitor, 2005 Volkswagen Passat TDI, 151,000 mi
Water keeps appearing in the rear footwell on the drivers side of the car every time it rains. (Left side). It damaged my module. The (water tight) box under the carpet of the drivers seat (left side) North America was completely full of old rusty coloured water. The module and 2 plugs were a blue ish green colour. Completely corroded. My power windows and locks stopped working completely. 3 of my windows were stuck down 4" or so. I couldn't raise them up or lock my doors for days until I got a new module box and 2 plugs from a vw wreckers yard. This problem has caused me continuous headaches. I've heard it's a common problem with 2005 vw passat wagon tdi's. Could it be a clogged sunroof? Or any other recommendations from anyone? I'm very tired of constantly finding a puddle of water in my rear footwell. VW should be ashamed of themselves.