The heater blower for my 97 E420 works at 1 speed only (low) no matter what the display shows. Could the blower motor voltage regulator be bad and if so how do I replace it?

 

most likely its the blower regulator which is attached to the blower. but if you car is older you might need to buy the blower and regulator and the blower cover all together because of a design change. your 97 might fall into that. a MB dealer will tell you if you need that. unless its already been installed in the past.