My car is only blowing cold on the right side , blows warm, not hot on left . It is warmer than regular ambient air so I'm thinking that an actuator stopped working but I'm not sure which one to check first. Any Suggestions?

 

Update... The left side all of A sudden started working, blowing cold, and I thought that maybe it was just A glitch but when I went to use heat / defrost it would blow cold out of the left and heat out of the right. Its obvious that whatever controls the temperature on the left side is either sticking ir intermittently working. Does anyone have info as to where the actuator is located that controls the left side temp regulation?. It was cold this morning and thank God I have heated seats!