Vents only blow out floor and defrost


93gmcjimmy
10-29-2010, 02:36 AM
'93 GMC Jimmy 4x4. My vents only blow out the floor and defroster no matter the setting. The A/C and heat work fine just can't switch to any other vents. I hear a hissing behind the dash all the time and even for a minute or so after I turn the car off. Any ideas?

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