1998 C230, 73K miles... with AC on, air flow from center dash vents frequently is redirected to foot well vents, particularly, but not always, during hard acceleration. After a few seconds, normal air flow resumes from center vents. Any ideas as to the cause?

That happens due to loss of vacuum to hold the a/c flaps open..most likely a fresh air diaphram

Either have someone test the vacuum system /// try pressing the [EC] button & see if they stay open..

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