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 W8 Water From Clogged Sun Roof Drains May Damage Control Modules
Volkswagen Passat W8 Problem
Average Mileage: 100,717 mi (46,000 mi - 165,000 mi)
Visitor, 2002 Volkswagen Passat W8, 46,000 mi
I had this problem too. Make sure your service station cleans the weep holes and tubing that discharge the water from the sun roof gasket to the street every time you get the oil changed (dealerships seem to do it as part of the standard oil change service). I have covered the gap between the sun roof and car top with clear duck tape to keep water from getting to the gasket.
I was lucky because my insurance covered $1,900 of the cost of the repair and replacement of the comfort control module that was shorted out. Most of the cost was for labor because the front seats and most of the passenger cabin has to be removed to get to the module.
Visitor, 2002 Volkswagen Passat W8, 135,000 miRookie
Noticed the interior floor was flooding every time it rained. After taking it to several repair shops then having it checked at a windshield replacing shop. Luckily the worker was able to find the actual problem which was the sunroof drain was clogged causing the water to build up and spread throughout the car, mostly the carpet on the floor and glove compartment. In the winter time, anything electric (i.e. radio, odometer, dashboard lights etc.) will shut off while driving. Assuming that the water is freezing up and is damaging the control modules. Still working on fixing the trouble & replacing all damaged parts.
Visitor, 2003 Volkswagen Passat W8, 88,000 mi
clogged sun roof drain caused water to drain into my car and has caused problems with my control panel
Visitor, 2003 Volkswagen Passat W8, 108,000 mi
Still haven't been able to find anyone to fix the leak.
Visitor, 2003 Volkswagen Passat W8, 96,020 mi
The Florida heat caused the drainage lines to melt closed and the water backed up into the car. My floor was wet for a few days before I realized it. I have had electrical problems ever since.
Visitor, 2002 Volkswagen Passat W8, 67,000 mi
bad VW. Never again will I be fooled into buying one. Dealership too expensive.