Batteries are in correctly. I was curious and double-checked that earlier this afternoon. I don't think the display will illuminate if they're in wrong, but no matter, they're in ok.
No bent pins. They all look straight, true, and show no other signs of trouble such as corrosion or being loose/wobbly on the circuit board.
FYI - I can hear the trigger mechanism click when the temperature reaches the desired set point, but nothing happens. (The furnace does not come on.)
I've tried to test the unit the same way in "Cool" mode following these steps: 1) Switch the Thermostat to the "Off" position and then wait a few seconds. 2) Switch it to "Cool". 3) Bump the current "Temp Setting" to current room temp and then a degree more (if the trigger has not already clicked). But in "Cool" mode, the thermostat will not trigger (click) no matter what the programmed temp setting is changed to, on, near. above, or below the room temp
I don't understand why in "Heat" mode, every time the temp setting is changed (bumped a degree at a time), as soon as it reaches the current room temp the unit triggers (clicks) immediately. In "Cool" mode it won't trigger that typical little click at all.
I have turned "off" and back "on" all circuit breakers connecting all components. Nothing seems to make any difference.
Thanks for your input thus far.