I located this unit under the dash, passenger side of my 72 Maverick 4 door. It was unplugged and when partially plugged in, the unit vibrates and buzzes. I am trying to get my interior fan switch to operate the different speeds again but came across this. Also, if anyone has a recommendation on what to check for my fan speed selector not working anymore, that would be great. It just stopped working one day a couple years ago. I replaced the red resistor on the blower housing and that didn’t fix it.