I have a 2004 Gmc Sierra 1400 SLE. It has the manual dual climate control. Both work outstanding on A/C.. When the Heat is on both the passenger side blows heat while the Drivers side blows cold air. Called the parts house they told me it could be the main blend door actuator or the auxillary actuator. What is the difference? Also my mode switch doesn't switch between the different vent modes.... if I have the recirc button on and switch it to defrost the amber light will go off on the recirc button. Which tells me it is reconizing its in defrost just the doors aren't moving. What would be causing all this. Any help would be greatly appreciated. Thanks in advance

 

The actuators are plastic with plastic gears. They go bad after time. We have all had problems with these.

 

it is clicking from the actuator on the driver side.... would that same actuator cause my mode to not change on my vents?

 

If it is clicking, it is bad. There is more than 1 actuator. They serve different functions.