I installed the Aux fan last weekend. The new fan is now kick on when the AC first on. I bought the Dorman 621-213 Harmonic Balancer and it perfectly fit. Took me half a day to finished the job.

__________________
2003 X5 4.4i w/ Sport Pkg, Cold Weather Pkg.
2010 X5 4.8i w/ Sport Pkg at 19,000 miles