Strange new development with heater that was stuck on

I posted a question here on April 1 about the car heater being stuck on “on” and blowing hot air at full force. The display panel and the push buttons and knobs that control the temperature and location of air flow were not working at all. The next time I used the car, the heat was off but the heater/AC was still dead (display was dark and buttons & knobs not responding). Well, today I used the car locally to do some errands and – lo and behold – after driving for a few minutes, the heater/AC was back to normal: the display panel now lights up, the controls work, and both hot and cool air are produced.
Any idea why this would magically fix itself?

Is that one of the Concordes that had automatic temperature control? If so, the control computer is known to sometimes go nuts and do weird things. You sometimes have to reset it. They also have a self-diagnostic feature you can use, but if I recall the method for activating that feature changes depending on the year. Post details on your car and we might be able to find you some test procedures.