Air duct flap will not go to the defrost postion.

Chevy vents are designed to be a perfect mouse house, they always build a nest near the heater blower and you have to weasel out the blower housing by prying up the unidash under the glove box, after removing the screws (make sure it is in the off position).

My 94 did this and I replaced the Mode acuator under the drivers side dash ... Defrost works fine now...