Turn off the power to the HVAC system at the breaker
Remove the thermostat cover
Take a photo of the existing wiring
Label each wire by its terminal
Disconnect the wires from the old thermostat
Remove the old thermostat base from the wall
Check the wall for damage or loose wires
Mount the new thermostat base
Pull the wires through the new base opening
Connect the wires to the matching terminals
Attach the new thermostat display or cover
Restore power to the HVAC system
Follow the thermostat setup and configuration steps
Test heating and cooling functions
Secure the thermostat and clean up the work area