blend door actuator

my 2003 gmc savana only blows cold air. It started last year, it would blow hot air off and on then it quit altogether. Is their any way to test the door actuator? Any ideas would be greatly appreciated. Thank you, Chad

I am trying to install a new heater blend door actuator in my 1997 Jimmy. The actuator that I removed has 6 pins for the electrical connection, but I only have 4 wires attached to the wiring plug. My new actuator only has 4 pins, BUT, they do not match up with my wiring harness. From what I...