Front AC Unit Heater/AC Gate not working

I've got a 95 4WD 7.4L Suburban 2500 and cannot get the front AC to get cool. The rear AC works great and I've been told that there is a gate that directs the airflow across the heater core and the AC "core" and mine is stuck somehow. How do you access this gate and is it electrical or vacuum operated? Any ideas on how to get this fixed?

I beleive it is electrical and you have to access it from under the passenger dash.