Sounds like B-line's dealer confirmed what I was thinking about the shortcomings of the rear climate control setup/fan. He also mentions another climate control issue not related to the rear system - that is that the outboard front vents have much less airflow than the middle vents. I have to partially close the middle vents to balance it out.

To the OP, I'm not suggesting any of this is a reason not to get the ZRC. As others here have posted, there are plenty of useful benefits of the ZRC. But if you live in a hot climate, expect the overall climate control of the X5 to be disappointing as the rear system works at the expense of the front passengers.

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2008 X5 4.8i, Jet Black, Tobacco Nevada leather & just about everything else (no vent. seats, no 3rd row)