[dcb]

The regulator has to dissapate about 1/4 of a watt. putting it in a box means some thought has to go into ventilation. Putting it in a black box in the sun is really challenging it.

But if its working now it is working. An occasional freeze isn't that unusual, I've witnessed a couple but they were few and far inbetween, so wasn't anything I could effectively troubleshoot.

edit: I did notice some verbiage in the latest datasheet about a built in cpu temperature sensor. I may have to look into that, if only for display purposes. The sheet lists 85C as the peak temp for the cpu.

edit #2, the crystal lists a max operating temp of +70C, 158F