There is no heater control valve. That was a valve that was in the heater core supply line and controlled the amount of coolant flow to control temperature. They have not been used in years. Your car has a "T" fitting in the line. If that T has been removed or replaced it must be replaced with the restrictor in the same leg it was removed on or you won't have any heat. If that is not the problem, then it might be a clogged heater core or a failing air mix door actuator.
The t fitting is still in the line. Where is the air mix door actuator? Is there any way to test the core without removal? I purchased a Chiltons and ended up returning it because it failed to provide any problem solving tips. In fact the heating system was summed up in a page without any diagrams.
blend door can be seen by pulling the glovebox out which is easy. Just remove the 4 or so screws inside it and the couple on the face and it slides out in one piece. run the temp between 60 and 90 and you should see the door move. then as suggested make sure the t-fitting has the restrictor on it. Should have an arrow on top pointing toward the passenger side. If you have no luck I have a heater diagnostic page I got elsewhere on the forum that I may be able to dig up.
Sorry to bump an old thread, but I have a question regarding the Tee in the coolant hose line behind the motor.
I have a 93 Sedan DeVille with heat on the passengers side floor and dash vents, but little/no heat on the drivers side. I checked the Tee for the coolant line and I had a rather generic looking Tee with no restrictor, so I got a coolant control valve from O reillys.
I believe the heat has improved, but I am still only getting heat on the passengers side. I have the arrow of the new Tee facing towards the passenger side. (EDIT: Clarification, the restrictor is towards the passenger side.) Could my heater core be partially clogged, the tee on backwards, an actuator under the dash not functioning properly, or should I put the old Tee back on?