In design aspect that can't happen. In auto mode it's either cool or
heat, not both. ASIC can't do both at the same time.

Well, I'm no EE, and "Don't turn on heating and cooling at the same
time" would seem to be something rational beings would want to
implement at a pretty fundamental level when designing thermostats, so
unless somebody else comes along and says differently, I'll take your
word for it

But if the the article is correct, and a properly connected thermostat
was energizing both, it would be interesting to know what mechanical,
electrical or electronic defect was present.

I've submitted a request to Honeywell Tech Support for additional
information on this problem, if I get an answer, I'll post it.

Michael Thomas
Paragon Home Inspection, LLC
Chicago, IL
mdtATparagoninspectsDOTcom
847-475-568