123 Hot Center Vents

[OM616]

Vehicle is a 84 W123 300D. It has all heat or all cool out of all the vents.

I have been trying to figure out why I am getting hot air out of my center vents when it is trying to lower the cabin temp. The climate control seems to be doing its part controlling the fan speeds and when the cabin temp gets above the setting the center vents start to blow air, except instead of being cool air it is hot.

If I turn the temp wheel all the way to cool and the switch clicks, the hot water supply is cut off and the air coming out of all the vents will cool off. If I turn the wheel back the air gets hot again.

The vacuum diagrams that I have seen do not show (or call out) the heater core and evaporator doors. I am trying to figure out what is going. I am thinking I can override the center vent controls so I can get cool or hot air out of the center vents. I have the hot, I just need the cool.

Anyone have any idea what is going on?