I had this problem on my MY90 several years ago so this info isn't fresh in my mind but I called Gordon Kilebrew and we were able to resolve it. One of his tricks was to remove the blower motor resistor from the heater box. That allows you to look at a flapper that directs air to different positions. As I recall his advise was to remove and replace the battery cable and that causes the flapper to cycle and reset. His concern was that at least on MY90s was that the only thing to stop the flapper was the small tab that stops rotation had probably broken. Apparently repairing a faulty flapper is a royal PITA. Luckily for me it rotated and stopped as it should. From there we determined that the HVAC controller was the problem. I found one on eBay and I don't remember that it was a zr1 specific part. It is beside the steering column behind the hush panel and in its own right it is a PITA to replace. That did work for me and all these years later I've had no more issues. Gordon said that if the head unit doesn't see the return signals that it expects it just locks.
Like I say this if I went through this five days ago instead of five years my memory might be better but I do remember Gordon originally was concerned that the flapper just going around and around. Hope this helps.
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