One or more heater & AC (HVAC) temperature and/or air delivery mode door actuator may fail, resulting in improper temperature or air delivery. If this occurs, fault code(s) should be stored in the HVAC control module which should assist in diagnoses.Google+
Car Problem Reports
GMC Suburban 2500 Heating and AC Temperature and Air Delivery Mode Door Actuators May Fail
GMC Suburban 2500 Problem
Visitor, 1999 GMC Suburban 2500, 225,000 mi
the only location I got air is from the floor, if I unplugged one of the other actuators and left the fan off I could control where air would go, then I unplugged that actuator and can run the fan as normal. replaced both blend door and main actuators. will replace heat controller actuator this weekend.