You have excess moisture in the air, and it will condense on the windows immediately if the glass is very cold.

The source can be either water hanging in the AC box, a leaking heater core or core manifold, or in the interior of the car. You might want to pull the carpets up and check for water (and fix the leak if there is any). This could be from a sunroof or window left open in the past, too.

A leaking heater core will also leave glycol on the windshield, usually.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!