How to replace 1992,190D and 1989, 190E wiper assembly.
 

Put the hood up right position. Remove two rubber guards. To remove the screen situated below wiper, unscrew two screws at each end of the screen. Gently push downward or slide down away from windshield and then lift it upward on the other side. Now the whole wiper assembly is exposed which consisting of linkage and an aluminum bracket. Unscrew two screws (10mm) that mount the alu. bracket, one on each side of the wiper turning part that hold the wiper rubber blade. In order to remove assembly, the nut that holds down to wiper motor had to be unscrewed. Attention here!!!!! It's a 13 mm nut, unscrew it anti- clockwise, so doing it would turn the wiper as well, so use a spanner clamping the linkage to counter act so that nut could be loosen. Now remove assembly, there is not much room, use common sense and slide it out assuming that the motor is working without having to remove it.
Please pay attention here when putting assembly back in place: You would wonder which position of the wiper you should put it back. Mount wiper assembly by mounting the two screws. Here is the trick, turn on the key 'on' position, turn on and off the wiper switch as you would, this action would put motor in returned position. *Next move wiper arm to the lowest position on windshield which is also returned position. Put linkage onto motor bolt that has a taper with straight grooves, MAKE sure the hole is absolutely in center of bolt and surface is 90 degree, then push it down and tighten it tightly, otherwise, it might slips and grinds off those grooves and malfunction the turning blade. I hope this is clear and would help someone fixing one's wiper assembly replacement. Put the screen back and tighten it with screws. Happy working!