German engineers designed the entire automobile around the heat blower motor, located at exact geographical center of the automobile buried behind the dashboard up against the firewall.

Mercedes legend and lore says that craftsmen assembling the finest sedans in the world started with heater motor and attached unibody frame, suspension, engine, drive train and finally the interior appointments all around this simple component.

Modern MB's from the early 1980's include automatic climate control....... an insanely complex system of sensors, relays and vacuum servo-switches that nobody can understand. On more primitive late 1950s and early '60s versions, heat blower motor was luxury addition that was bought as extra feature such as sunroof and AM/FM radio.

If it was me, I'd first check the dial switch that activates the heat blower motor...... then pray to god the fan motor itself does not ever need replacing.