M.B.DOC,

I’ve been driving around with the bottom part of the dash off and until yesterday I’ve not had heat when the temperature control knob was turned all the way to the left. That's the way it should be.

Then yesterday I had heat when it was turned to the left. I looked at the linkage and the arm for the blend air motor was not where it should have been it was positioned to allow some heat. I have no idea why the blend air motor did not return the linkage to the position where it does not allow heat. I have no clicking or other noises going on. Is this indicative of failing blend air motor?
Is problem blend air motor, temperature sensor, something else? Is there a way to test whether or not proper signal is being sent to blend air motor?

If not then I'm thinking it be best to replace both blend air motor and temp. sensor, since I think I have to take evaporator box/case apart.