99 GMC Sierra 1500 - top dash and floor vents inoperable

I have a 99 GMC Sierra 1500 w/5.3L with 98k miles. Has anybody experienced problems w/the top dash and floor level vents becoming inoperable?... they don't blow regardless of the fan speed selection, recirculated / fresh-air
setting, or the temp. control setting (hot or cold). All of the front dash vents operate properly.
Does the vehicle's air circulation system have multiple fans which could fail?
Any info. is appreciated. -pup
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You only have one fan motor. It sounds like either the small motor that moves the flapper door (air valve door) that changes your vent positions inside the duct work has failed or is stuck. When you change vent positions from heater (foot level) to dash to defroster do you hear any humming or soft buzzing from under the dash that tells you the motor is working or trying to change the air valve position but is stuck?
Cheers - Jonathan
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Jonathan A. Race
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Thanks, Jonathan for your reply. I'll take a listen under the dash. I haven't heard any "noticeable" humming sounds when I change selections from heater to defroster, but I'll take a closer listen... with my luck, the flapper motor has failed.
Thanks again, -pup
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With luck the motor isn't burned out, just the flapper door is stuck in one position from some gunk. If that's the case you may be able to just get in far enough to reach the door seals and clean them off.
Cheers - Jonathan
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Jonathan A. Race
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