why does my sensi touch keep switching from 'heat' to 'off' by itself? i didn't program that.

Diagnosis

The Emerson Sensi Touch ST75 is designed with "Smart" energy-saving features that can override manual settings. When the thermostat switches from 'Heat' to 'Off' spontaneously, it is almost always due to a logic conflict between the physical interface and the cloud-based settings in the Sensi mobile app. Specifically, the device is likely triggering an "Away" or "Eco" mode. This happens when the thermostat perceives that the home is unoccupied, causing it to drop the system to a baseline "Off" or "Energy Saving" state to prevent heating an empty house.

This behavior is typically triggered by one of two things: a programmed "Away" event in the weekly schedule or the Geofencing feature. Geofencing uses your smartphone's GPS location to create a virtual perimeter around your home; when your phone crosses that boundary, the Sensi Touch receives a command to switch to a pre-set "Away" temperature or shut the system off entirely. You can confirm this by checking the Sensi app immediately after the switch occurs; if the screen displays "Away" or a leaf icon, the software is overriding your manual input.

How to Fix It

To stop the Sensi Touch ST75 from automatically switching to 'Off', you must disable the automated triggers in the mobile application. Follow these exact steps:

1. Open the Sensi app on your smartphone and select the specific thermostat that is malfunctioning from the home screen.
2. Tap the Schedule icon (the calendar symbol) located at the bottom of the screen.
3. Scan the current day and time for any greyed-out blocks or entries labeled "Away". If you find an active "Away" period, tap the event and select Delete or Cancel to remove the override.
4. Exit the schedule menu and tap the Menu (three horizontal lines) in the top left corner.
5. Navigate to Settings and locate the Geofencing menu.
6. Toggle the Geofencing switch to OFF. If you wish to keep Geofencing active but stop the "Off" behavior, tap Away Temperature and change the setting from "Off" to a specific temperature (e.g., 62°F) so the system remains in 'Heat' mode rather than switching to 'Off'.
7. Save your changes and restart the thermostat by removing it from the wall plate for 10 seconds and snapping it back in to refresh the cloud synchronization.

If That Didn't Work

• Check for Third-Party Integration: If you have linked your Sensi account to Amazon Alexa, Google Home, or Apple HomeKit, these platforms can trigger "Scenes" or "Routines." For example, an Alexa routine labeled "I'm Leaving" may be sending a command to the Sensi to turn the system off. Check the "Routines" tab in the Alexa or Google Home app and delete any automation that targets the thermostat.
• Verify C-Wire Stability: If the thermostat is losing power momentarily due to a faulty C-wire (Common wire) connection, it may reboot into a default "Eco" or "Off" state. Remove the faceplate and ensure the blue C-wire is seated firmly in the terminal. Use a multimeter to verify 24VAC between the R and C terminals; if the voltage fluctuates, the unit may be power-cycling and resetting its mode.
• Perform a Factory Reset: If a glitch in the firmware is causing the logic loop, perform a hard reset. On the device screen, go to Menu > Installer Settings > Reset. Note that this will wipe all WiFi and schedule data, requiring you to re-add the device to your network.
• Inspect the Touchscreen Calibration: In rare cases, a "ghost touch" caused by debris or a hairline crack in the glass can trigger the 'Off' button. Clean the screen with a microfiber cloth and a small amount of isopropyl alcohol to ensure no conductive residue is triggering the capacitive sensor.

Heads Up

• Always ensure your Sensi app is updated to the latest version via the App Store or Play Store; outdated firmware on the app can cause "command lag" where a setting you changed hours ago only triggers now.
• Avoid placing the thermostat in direct sunlight or near a drafty window, as extreme temperature swings can occasionally trigger "Eco" logic if the sensor thinks the room has reached a temperature that no longer requires heating.
• If you are using a heat pump, ensure your "O/B" setting is correctly configured in the Installer Settings, as incorrect reversing valve settings can sometimes cause the system to shut down as a safety precaution.
• Keep a record of your specific wiring configuration (take a photo of the wires before removing the plate) in case you need to perform a full factory reset and re-installation.