Thanks for the link, there was this comment:
…the problem is a switch that is soldered into a circuit board on the back of the A/C Controller Assembly. There is no practical way to repair this switch nor swap out any sub-assembly. The entire controller (which consists of the 3 rotary knobs and the 2 push-button switches) must be replaced. The switch fails in the same way a single button will quit working on a TV remote control. I purchased a used controller from a junkyard. The online parts manual shows that the original controller has been superseded by a new part number. I also noticed that my old one did not have any orange illustrations on the mode selector, but the newer one I purchased has matching orange illustrations for the fresh air knob and the defrost settings.
so a lot of work to a take the dashboard off, replace the whole unit, not just the switch, not an easy fix