Coolant temperature light is on. Coolant level is full. The owner's manual indicates fuse may be out, but has no instructions as to how to check/install fuse. The Manual refers to page 170, but pages 153-190 are missing in the manual.
How to replace coolant temp fuse. on 1995 Volkswagen Passat
I would check the Coolant Reservoir Level Sensor, which do go out and when they do, they can set the temp gauge light. VW calls it the Expansion Tank, it goes for about $60, but first try disconnecting the sensor ( it is a 2 wire connector on the bottle) and see if that turns off your light, then you will KNOW.