A malfunctioning HVAC blower motor regulator can cause the blower motor to operate below the requested speed or not at all. Updated regulators are available; the blower motor and cover need to be replaced at the same time to upgrade the system.
Car Problem Reports
Mercedes-Benz E420 Malfunctioning Regulators May Cause Blower Motor Failure
Mercedes-Benz E420 Problem
Model Year Affected: 1997
Average Mileage: 115,000 mi (99,000 mi - 135,000 mi)