If my memory is correct, it is behind the intrument cluster (for the '82 300SD, 300D is different). The early 300D (1981? or older) has the relay (for emergency and turn signal) as part of the hazard warning switch. Many time, someone touches the hazard warning switch and the switch is not pushed back all the way to its orginal position causing the turn signal not working. I saw one case that the owner turned on the emergency lights for long time and burned the hazard warning switch causing the turn signal not working. Did anyone play with your switch lately?