Not sure what you are saying, but here is how it works:

There are two menu settings in idrive, one says "enable rear controls" which allows the rear passenger to make climate adjustments independent of the front system when selected. When unchecked the rear system is turned off.

The second option says "use driver settings" when this is checked the rear system uses the same settings as the front.

The rear controls have zero effect on the front...it is not possible for the rear seat to control the front climate. Both fans are in the front dash though, so I think you are just confused by the sound of the rear system in the front dash.

I keep both options checked and dont let the kids use the buttons, because it overrides the second option.

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2013 X5 35i M Sport