A video describing the operation and how to diagnose a non working blower motor on a Nissan or Infiniti vehicle. Same principle applies to many other makes.

LED test light: http://amzn.to/2lbHYt3
Power Probe 3: http://amzn.to/2lbFHyc
Oscilloscope that i used: http://amzn.to/2mpXHGX