W210 Blower whine?

My climate control has a high pitched cyclical whine but usually only when the passenger side has air directed at the feet. When on defrost it's normal, and on the driver side it doesn't whine if I select feet as well. I
originally though it was a blower motor but if there is only one blower motor, and it's well behaved on defrost, what should I be looking at to diagnose the high pitched whine? Thanks.
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It's the blower motor. Defrost is the highest blower speed and may not indicate the worn out bearing on the blower motor. When you select the "feet" , as you state above, the blower speed is slower and the sound is more evident. As time goes on the whine will get worse until you replace the blower motor.
Good Luck
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I
Wow .... you have a supercharger in the climate control !
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