Transmitter / receiver (interior motion sensor), location - GF80.50-P-4104-01A

Models 140, 202, 208 (except convertible), 210.0 up to 6/98, 210.2 up to 6/99 with code 882a 

Illustrated on model 202 T-model 

Fig 1: Identifying Transmitter / Receiver (Interior Motion Sensor) Components Location

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.