My fan seems to be stuck on vent. I think the flap that switches from defrost, to heater on the floor, to the vent must be stuck. I can turn it off. I don't think it is the switch. Can any one tell me where this flap is located on a 1999 GMC Jimmy 4X 4? Any help would be appreciated.

i think its the actuator..i just replaced mine today ouch lost all kinds of skin...lol