I think I read others were having this issue a couple years back, but I cannot seem to find the threads.

I cannot get warm air at all until the temp setting is at 90 degrees. If I turn it a click down, the air is cold again. Is it the heater blend motor or whatever that thing is called?

 

There is a mix valve under the hood near the fire wall on the passenger side that's cable operated. Have someone adjust the temp from hot to cold and see if it changes/moves.

 

My Solara had a problem some what like that before. The heat won't turn on low, can only be turn on high speed. I changed the thermo resistor and problem solved.