If you have a coolant leak into the interior air passages, you should smell it (like an overheated radiator smell). Actually, your description sounds pretty normal to me. You are putting the warm (and more moist)air away from the glass, leaving the glass surfaces cold and excellent surfaces to condense out moisture carried in by the warm air. Some systems don't allow all air to be cut off from the windshield, just for this reason, but I believe Volvo's do cut it all off if you choose to. If you run the Ac compressor, it would reduce moisture coming in with the warm air, but easiest is probably just to keep some air going to the windshield when it is cold.
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Mike Sullivan ('91 745 (171k), '93 965 (147k), '95 855T (60k), '98 V70XC (78k)