I took a good look at my 2006 4.8is and it has only one fan, and it is behind the radiator. Your link to RealOEM shows that fan. There is no engine driven fan and no Aux fan. So I guess the 4.8is is set up a bit differently. I am having the same AC symptoms I have seen in other posts in the forum, AC won't kick in unless the engine is revved around 4K, so probably low Freon. I did get a bubble in the Schrader on the high side when I removed the cap, and the engine was not even running.

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2006 X5 4.8is