So first things first, I live in a condo. I don't have a lot of easy access to my AC (and I would imagine my furnace? I'm only guessing where that is though it might be near the water heater instead). But I'm really hoping someone here knows what's going on.
I have a Honeywell TH1100D as best I can figure. It's an old thermostat, came with the condo-- they were discontinued back in 2013. A couple weeks ago I had the fan-- no AC, and went for a walk. When I came back the fan wasn't running and the thermostat was completely blank. I found that odd, but assumed it was a temporary issue. It's happened once, maybe twice before and came on after an hour or two. But this time it never came back on.
I took the cover off to see if anything had come loose and noticed that there were no batteries installed even though there was a spot for them. The solution, I thought, was obvious. It's not getting power, supply it with batteries. I popped two batteries in and the thermostat came back to life! But when I put it back on the wall it still wouldn't trigger the fan or the AC. I popped the batteries back out again and went to hang it back on the wall when I happened to notice the fan trigger for maybe a tenth of a second while I was putting it back in and then turn off.
After some finagling I managed to have the thermostat tilted at such an angle not-quite-fully-seated that it would kick on, cool the place, and everything worked. A bit janky, but certainly not the hackiest thing I've done. It worked well for a couple days but suddenly went off. I tried to get it back into position but it's become IMPOSSIBLE to get back. Now, I can only hear a brief "click" of it getting power not even enough to activate the thermostat before it dies again. Batteries still work, but it still offers no control.
I removed the back plate and gave the wires/contacts a brief hit with a wire brush I had, assuming there might be some corrosion, but that doesn't seem to fix the problem.
Does anyone know what might be going on or what I should do to fix it?