Just bought the Blower Motor for my 1977 450SL. I know that my old blower motor is bad. I bench tested it by running a pos and neg wire from a 12 volt battery directly to the motor. The motor will not spin. I did free it up but it still does not work. I do have a question. How do I know that the 4 speed blower switch at the dash is working properly? Also, how do I test the module the plugs in to the blower motor? I know that I am getting 12 volts to it but how and where do I test the speed variance on the dash and the module at the blower motor? Any help is appreciated.