my 2000 sts w/75000k only gets cold on the passenger's side. (AC) it's like something is not closing or opening to let cold air into vents on driver's side. any help is appreciated.

 

I'm not a mechanic and it sounds to me that you should get the car checked with a diagnostics machine. It's about $60 and you'll check all the sensors for you. That's an easy way to see of something is not working with the electronic side of things. If it turns out everything is ok in that side, then you have some work ahead of you. (or spend big $)

Maby one of the control valves is not opening all the way and allowing the gas to circulate through your side side. Which will require you to get to the heating system.

 

its the driver side mode door actuator
needs replacing