Early this morning was the first time I had put the heat on in the X. I noticed what sounded like some sort of aux motor running on the pass side of the engine. Ran for about 20-30 seconds then winded down. What is this? Is it something silly i'm just overlooking? I know the A/C motor runs at times to help defrost but it wasnt that.

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03' X5 3.0i auto (9/03)