1998 Nissan sentra ac bypass - 1998 Nissan Sentra

Assuming that it is working in frigid conditions, sometimes The
Ac works with the defroster to remove moisture and the fog on the inside windshield. So, turn the defroster of unless you need it when the windshield fogs. You may be able to keep the window clear by opening the outside air vent and increasing the heater temperature.