I have a Honeywell honeywell prestige thx9000 thermostat which has a cr2032 battery. It is wired with the IAQ interface and uses the R and C wires at the thermostat. It works great without inserting the CR2032 battery. However, when I insert the battery (which is suspose to ensure settings are kept in the event of a power outtage) the thermostat screen will not turn on. All I see is black. I've used a few CR2032 batteries to eliminate the possibility of a low power battery. All the rest of the components work perfect including the wireless outdoor sensor and the remote handheld thermostat control.
Any thoughts? Thanks in advance.