Hi Bill: Thanks for the reply
The airflow thru defrost vent is slightly higher than ( or may be almost equal to) the air flow from the central vent.
So where do i start. What sequence of checks or repairs I have to do?
Do you know the location of the air contol unit that may be causing this problem?
I am new at AC controls.
Thanks
MVK

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1985 300D Turbo 179,000miles