Thermostat not charging. Gives error 73, but already check all.the wiring, is good, plus it's doing this on and off for about 3 days. If it wasn't getting electricity from the wiring, it makes no sense to be an on/off situation.
It could be your AC unit causing the problem. Check out this post from a few years ago regarding a problem with the AC float switch shutting off power to thermostat because of blocked condensate drain.
