mac,can you apply power to the old & new motor to verify if they're good and were mistakenly replaced (nothing simple in a 12v vehicle will "Blow " a new motor ) chances with two you know. Remote possibility is Detailers dropped something which caught it'a way imto the "squirrel-cage" vanes of ea. of the motors - stuck in the vent passages not visible and keeps dropping & jamming motor?
mac,04pathse - good point = next likely it's right at the control center that may be broken and AGAIN gotta ask yourself "Did I replace a working motor? " Gave those two motors a "Jump" yet ??