Turn off power to the HVAC system at the breaker
Remove the thermostat cover if it has one
Check the bottom or sides for release tabs, screws, or clips
Loosen and remove any visible screws
Gently pull the thermostat body away from the wall plate
If it is snapped on, press the release tabs and lift it off
Do not pull hard on the wires
Label the wires before disconnecting them
Disconnect the wires only if needed
Remove the wall plate screws if you want the entire unit off the wall
Keep the wires from falling back into the wall
Restore power only after the thermostat is reinstalled or the wires are safely secured