My wife reports a new problem. The windows (all windows, not just the windshield) will fog up. They can be cleared by setting the control panel to defrost, but she swears this was never necessary before.
I am at a loss to understand how the automatic climate control would know when defrost was necessary. Looking at the manual, the system has a sunlight sensor, passenger compartment temperature sensor, and outside temperature sensor. Perhaps there is some combination of inside & outside temperature that causes the defroster to come on????

Since this affects all windows, I don't think the problem is the heater core. There are no flashing lights on the climate control to indicate a fault.