Our TH8000 Series Programmable Thermostat keeps flashing "change filter" even after we changed it. The guide book does not show how to re-set so the flashing stops.

The issue is probably not the thermostat. The thermostat is a series of switches that turn on and off in respect to the temperature. Since it takes batteries and installing those made no difference there is a chance that a relay is stuck in the furnace or the thermostat. I have attached the testing and installation guide for you to look at. Honeywell VisionPRO TH8000 Series Installation Manual Installer System Test

Was it also very humid that day? The evaporator coil may have frosted over if that was true.

sounds like keypad is programmed in lock position read manual for set up to activate keypad again.

Google " vision pro installation manual" download pdf.

If you need further help, reach me via phone at https://www.6ya.com/expert/thomas_092728000e6acb79

if you have a heat pump you must go to installer set up and change the reversing vave to energize in cooling

Mystery message "wait" appears above "following schedule" display line on our Th8000. Ac does not come on even when temperature is in range. Fan operates ok. Is "wait" setting one I can reset? Maybe a compressor issue rather than thermostat? Thanks

Try setting the fan to Auto.

Are you saying that the filter indicator on the thermostat screen is flashing filter? If so this feature is built into the thermostat as a reminder. It can be set for 30, 60, 90 days to remind you. It also can be turned off. Of course the air filter is in the cold air return, or blower compartment of your furnace.

Is the thermostat mounted near a lamp or other heat source?
Is the wall warm from ducts in the wall or a refrigerator on the other side?
The thermostats are usually pretty accurate. Most times I find some other influence on the thermostat causes the problem.
The Honeywell 8000 series also has a feature accessed through the installer setup menu, that will allow the temp display to be changed + or - 8 or 9 degrees.
Check the manual or Honeywell's website for a .pdf if you need it.
Hope this helps.
Matt

The thermostat has a function called "Adaptive Intelligent Recovery".

This feature allows the thermostat to learn how long the furnace and air conditioner take to reach programmed temperature settings, so the temperature is reached at the time you set. For example: Set the Wake time to 6 am, and the temperature to 70°. The heat will come on before 6 am, so the temperature is 70° by the time you wake at 6.

You can turn off this function. Download the installation guide at the next link:
http://customer.honeywell.com/honeywell/ProductInfo.aspx/TH8321U1006
and look for funcion number 0530 Adaptive Intelligent Recovery. In this manual you also find the way to do a reset with the function number 0710.

I hope this solves your problem.