The Volkswagen Golf IV refers to the model years from 1998 through 2005. The body and components did not change over the production run though there were some changes in available equipment and trim levels. Changing a tail light in a 1998 or a 2004 is no different on these cars. Replacement bulbs are available from most auto parts stores for your Golf.
Open the rear lift gate of your Volkswagen Golf. Locate the trim panel inside the cargo area of the car just inside the hatch opening.
Locate the two round fasteners on the trailing edge of the panel. Turn them anticlockwise to unlock them and remove the panel to expose the rear of the tail light assembly behind the panel.
Locate the bulb holder running up the centre of the tail light assembly. There are two retaining tabs on the holder, one on each side. Squeeze the tabs in and pull back on the bulb holder, removing it from the rear of the assembly.
Locate the bulb that is not functioning, there are three inside the bulb holder, and push in on it slightly. Rotate the bulb anticlockwise then pull the bulb out of the holder. Discard the old bulb. Insert a new bulb in its place, pushing it into the holder and then turn it clockwise to lock it in.
Position the bulb holder back into the rear of the tail light assembly and snap it into place. Replace the trim panel and turn the fasteners clockwise to lock the panel in place.