A/C and Heat work fine, but they only seem to be operable on Auto and Front/Rear windows settings. Pressing the buttons for Mode, Fan powers, and dual control do nothing. The passenger side temperature is stuck at 85 and won't come down (it was able to go up since I was able to press it to 85) so its always blowing hot air when on. Once again the dual mode button isn't functioning to take it off.

Is there some sort of button combination that could be pressed to reset the unit, or would it be best to have a Lexus or Toyota dealership. I'm not sure if a regular shop are used to doing things like this.

2001 gs300

 

Your thermostat is probably stuck closed or open, depending on if it's normally closed or normally open Thermostat..... Get a new one

 

If u need climate control i have one for sale,pm me if u need

 

Why would the thermostat have anything to do with the electrical climate control?

But see if you can find a used climate control. Or maybe borrow one from a friend's car to test it.