Hi. I gotta 05 neon sxt with a vibration from hvac fan when run on hi. the motors in good shape as is the shaft with no play. I had it out last time this happened and then worked fine for a few months. Only thing i see happen is a few pcs of a soft 1/2 in tape like substance, not really rubber or foam,have fallen from some where above . When u pick it up off floor it breaks apart..

 

some of the fan blades have a balance weight, are any of the blades broken?

 

none of the fan blades on the cage are broken and no weights. That stuff just falls from under dash.

 

could be just rubber chunks hittin the fan making noise then an not off balance, reach up in the area an feel around in there an see what you find. You can also power the fan motor while its out, hold it very tighty on the motor base and turn the setting on low to see if its out of balance just be careful that fan blade and take a chunk out of your finger. Might be best to hold it with both hands an have someone turn it on low.