Thermostat TH8110U1003, cooling mode with no outdoor unit just fan, heat works fine. My old stat works fine.?

Question

I am not using heat pump, just single heat/cool function. I know there is no problem with compressor because it works when old stat is wired. Any Idea? Heating mode works fine with my new stat (Fan and furnace works). I checked wiring R(24V heat), RC(24V cool), Y(compressor), G(fan), W(heat). Only wire not connected are O and B because I think it is not used (I dont have heat pump) and terminal C is not connected. I also tried each wire O and B simultaneously connected to terminal C on stat with no luck (also tried with both O/B together with no luck). Yes R and Rc are jumped and only using one 24V transformer. My new thermostat is TH8110U1003. Any idea?

Answer 1

Some t-stats have adjustments on the back of them you need to make for voltage , furnace type  check those make sure they are right and take the RC or R and touch it to the Y to see if the condensor comes on if it does not something may have happened to the condensor

Answer 2

sounds like you have it hooked up correctly.  Only thing I can think of is to hotwire the compressor (R,G,Y) with a wire nut and see if the comp fires.

you are correct that you should not need O,B.  C is to power your t-stat without batteries.

edit:  You have a vision pro 800 right?  There are lots of different ways to set up these t-stats.  Look at the instructions and it will give you 2 buttons to hold down to get into the programming menu.  There are numbers that correspond to certain settings.