This is not a totally foolproof way to check cells, and you are certainly right to advise folks to be thoughtful and prudent about where they put their faith. Obviously I haven't personally examined your home climate control system, so I'd be a fool to spout off and tell you there's been a mistake. But I have to say that something seems amiss here.

I don't mean to insult your intelligence, and if you know your stuff and are certain about what happened, please forgive me. But in case you're not too familiar with HVAC and are just guessing, I want to give you a heads-up that the problem could be something else and you may want to be on the lookout. Although it appeared a "low battery" was your problem, it could be that the fresh battery, (or the some aspect of the battery change) just masked or reset a different problem.







I am not an HVAC pro or guru; my observations are not definitive. Prelude over. There are two things that seem unusual to me, and here's what I can tell you. Although electronic thermostats do (usually, anyway) rely on their own power source to run their internals (including a switch that determines whether the furnace will be told to run), the actual messenger that switches it on is typically a ~5V line which is supplied by a transformer in the furnace. The thermostat's power just has to decide to close a little circuit on its board, which doesn't usually take much juice. Granted, that doesn't prove anything. The thing that bugs me more is thatit's usually a closed circuit that turns a unit on. Lack of power should result in a unit that fails to turn on.







I won't pretend that I can tell you what else could have been at fault for the "stuck on" condition, or even that I know for certain it wasn't just as you said. I just wanted to help out by telling you that from here it looks like there might be another problem lurking. If you know something I don't, I'd be happy to have you educate me.



Thanks, or you're welcome. Or both.

