My 94 940T. I was looking around at things to see if anything obviously needed attention, and saw that there is no heat control valve, at least in the standard place. In its place is a straight piece of tubing. No, this is not to bypass the heater core, that is still attached. It is only that the standard valve is not there.
Now, the car has heat. When I turn the knob the heat def comes on, and goes off when turned the other way. ???

I have noticed that the vent position switch has no effect; no change in what outlet, dash, floor etc get airflow. I also note that when I step on the gas, there is no airflow anywhere; then when normal pedal is achieved, airflow returns. I know that this is a symptom of a vacuum lack under the dash and is covered in the FAQ. I am wondering if anyone has a guess as to what may have been done in terms of the heat, and lack of change of ports.

I have not investigated under the dash yet.