Sierra lower temp servo problem!

[texasranger96]

Well I drove 50 miles home from KC with the damn heat on and windows open the ac has always worked good but it just went to heat and of course I had no leatherman so we drove all the way home like that I figured out it is the lower temp. servo and I got it to go to cold when I took it off and manually actuated but now I kinda got it moving so I don't know if it is the controls or the servo, the servo does seem to be strugling but I don't know how to ck it, so which one of these are the propable cause?

[PitchBlackC3]

If this is a 2003+, try this:
Turn the key on, do not start the car. Leave it on for 3 minutes, but do not touch the AC controls at all. Turn the key off and back on, see if it cleared up.

[gavin05]

gm has a relearn on the hvac system that should solve that problem

[texasranger96]

No it is a 2001 sierra I have prettty much figured out it is the lower servo I ordered it through oreily's hopefuly the controls are good, the older ones are alot more straight forward!

[texasranger96]

left to work tonight and the damn thing did it again sure wish I could get some help before I change the controls.

[classic1]

Is the servo vacuum or electric ?