This is a cross-post from another forum, but I figured I should share here as well.
I was out of the country for a few days, and happened to pull up my Sense app to check in on things. I noticed a really strange usage pattern: a 4kw load switching on and off every few minutes. After some thinking and looking at the load pattern, I decided my HVAC compressor must be cycling on and off due to a call for heat with no indoor blower running, hitting the high pressure cutoff, then repeating. Asked my neighbor to check it out, and sure enough, that’s what was happening. He pulled the disconnect and kept me from arriving home to a fried compressor.
Also noticed my Nest thermostat was reporting an unrealistically high indoor temperature. Did a little more digging, and apparently this is a common failure mode. Something shorts out internally, supplying constant voltage to Y1, and heating the baseplate up. So it appears i’ll need a new thermostat.
Glad I was able to catch this before 4 days of constant compressor cycling into overpressure protection.