Great! Thanks for the feedback. I copied most of the code for how the cooling is handling from another driver. I'm guessing that ekos could wait indefinitely for a cooler to reach the desired temperature. This behavior is outside of the driver so the best that I can do is to fix the driver so that it meets the expectations of ekos.
The threshold that ekos uses for starting captures after waiting for cooling is configurable in the options menu (kstars->Settings->Configure Kstars...->Ekos->Capture->Temperature Threshold). Mine was set to 1.00 degree C, so that probably explains what you saw.
I see the code that is causing the confusing/annoying behavior with the cooler. I'll see about fixing it later today. I think you're right about the intention of the buttons. It turns out that there's more subtlety to controlling a cooler than I though
For example, I'll fix the driver to allow you to set the target temperature to something higher than the current temperature...but will the cooler ever reach that temperature? I'm assuming that the TEC can't actually be run in reverse, but maybe it can? If Ekos is waiting to get within 1.0 of the higher target temperature then maybe it will wait forever?
I completely agree that this can, at least, work much better than it does now!
Also, I think the temperature conversions are still off a bit. It would be super helpful if you could capture a trace of setting multiple target temps in OCS. Maybe something like 30, 20, 10, 0, -10? You can do them all in rapid succession since I only care about the message that OCS is sending.
Your (previous) point about the camera not being able to detect the 12V presence makes sense and was something that I previously wondered about.