300SDL temp selector wheel

[pilot53]

Im having an issue with the climate control on my 86 sdl, the system seams to be working perfectly aside from the fact that the system doesnt maintain the temp on the wheel. I have tested the system according to the fsm, all of the doors and flaps work as they should in every setting, the system blows hot and cold air when it should, the blower functions as it should, the a/c is engaging, the internal temp sensor has the correct resistance readings and the aspirator motor is working and providing suction as well. The system will respond with changes in blower speed and air temp as I move the wheel, but its as if the system wants to maintain 75 degrees when the wheel is at the 60 degree mark.
Is it likely that something is wrong with the selector wheel itself? Are these serviceable?