Close works.controls work. control.valve.location? on 2000 Plymouth Breeze

First time this problem has happened while owner.unable to diagnose problem.need technical advise and guidance
what operates heater valve and where is it located? Car sat for 2 years not driven.

Asked by for the 2000 Plymouth Breeze
You have a plugged up heater core. See if you can find a shop that has the ability to flush out the heater core by it self. Otherwise it is a costly repair to replace it. The way the economy is now you will only find shops that want to replace it.
Merry Christmas, Jim