I have a 2006 Infiniti G35x. The heat/AC has been working fine till this morning when I turned the car on and put the vent control to high (on the front windshield). There was this awful rumbling and vibration coming from the dash for about 5 seconds and then I heard a pop/loud crack. After that, there was (and still is) no air movement within the cabin anymore. Neither the heat nor AC produces any airflow in the cabin through any vent. Is the fix as simple as a blower motor replacement?

 

It sounds to me like the rumbling/vibration noise was the bearing coming apart in the blower motor. Just pop the panel off underneath the glove box and there is 3 screws holding it in. Take her out and see what you've got. Just replaced one in a 07 model last week to be exact that was roaring.