On the 98, there is no block heater installed right out of the factory, so therefor, there won't be a plug. If you want a block heater installed, you can get ones that either magnet or glue to the bottome of the oil pan. I believe that this is the only option for the passat.
They are installed in holes in the engine block where the frost plugs are normally located
On a 3.4 liter engine the block heater plug is located slightly below and to the left of the exhaust manifold. You can access the block heater plug by reaching over the top of the engine or from the left side, under the alternator and belts.
haven't seen a block heater on VW's
If you have a 1999 Passat V6, the coolant temperature sensor is located in the lower radiator hose.
If the 1999 Explorer is equipped with a block heater, it will be located in one of the frost plugs in the engine. It is usually placed on the side of the motor that has the most amount of room to insert the plug.
left side behind the battery box
The heater coil is located behind the dash board. You will have to remove the dashboard to get at the heater coil
how do you remove a 1999 vw passat radio
Under the passenger side floor carpet.
It should be in the heater blower motor case which is located under the glovebox.
You'll find the heater blower motor resistor in the heater/air conditioner compartment. This compartment is location underneath the dashboard. This is the part that allows the heater blower motor to change the fan's speed.
The starter relay on a 1999 Passat is in the fuse box on top of the battery. It is on the top left portion of this fuse box and labeled as slot 'A'.