a/c control not changing position

i swapped it with the one out of my 99 silverado, it is the same except that the silverado does not have the rear window defrost button, and it made no difference. I repalced the actuator motor but that I found out is only for changing from heat to ac. I checked all the fuses in the dash and under the hood and all are good. Any further suggestions? I was looking at the repair manual for the silverado and they mention a resistor pack but I can not find where it is located, I suspect that it has something to do with the control.