the temperature reading is way off, it says 72 but my room feels like 65 and my other thermometer agrees

Diagnosis

The discrepancy between your Amazon Smart Thermostat's reading and the actual room temperature is typically caused by "thermal ghosting" or sensor bias. Because the temperature sensor is integrated directly onto the main logic board behind the display, it is susceptible to internal heat generation from the Wi-Fi chip and the power regulation circuitry. If the device is working hard to maintain a connection or if the backlight is frequently active, the internal temperature of the chassis rises, causing the sensor to report a higher temperature (e.g., 72°F) than the ambient air (65°F).

Another common cause is "wall draft." If there is a large hole behind the thermostat where the wires emerge from the wall, cold air from the wall cavity or attic can blow directly onto the sensor from behind, or conversely, warm air can trap itself in the wall box. To confirm if this is a calibration issue or a physical environmental issue, place a calibrated digital probe thermometer directly against the thermostat casing for 30 minutes. If the thermostat is consistently 5-7 degrees high regardless of the room's air movement, it is a sensor bias issue.

How to Fix It

To resolve a consistent temperature offset, you must utilize the Temperature Calibration feature to manually align the device with your reference thermometer. Follow these exact steps:

1. Place a known-accurate digital thermometer (such as a calibrated hygrometer or a medical-grade digital thermometer) on a flat surface directly adjacent to the Amazon Smart Thermostat. Wait 15 minutes for both devices to stabilize.
2. Wake the thermostat display and tap the Settings (gear icon) on the home screen.
3. Navigate to the Device Options menu and select Temperature.
4. Select Temperature Calibration. You will see the current reading and an adjustment slider.
5. Adjust the offset in 1-degree increments. If your reference thermometer reads 65°F and the thermostat reads 72°F, you need to apply a -7° offset.
6. Save the settings and return to the home screen. Note that it may take up to 10 minutes for the home screen display to update to the calibrated temperature.
7. Verify the reading again after 30 minutes to ensure the offset has held and the system is not over-correcting.

If That Didn't Work

• Seal the Wall Hole: If the reading fluctuates wildly or doesn't respond to calibration, remove the thermostat from the wall plate. Use a small amount of non-flammable insulating foam or plumbers' putty to seal the hole where the wires enter the wall. This prevents "chimney effect" drafts from the wall cavity from hitting the sensor.
• Check C-Wire Power Stability: Insufficient power delivery via the C-wire can cause the internal voltage regulators to overheat, biasing the sensor. Ensure your 24VAC transformer is providing a steady current. If you are using a power extender kit (PEK), ensure the wiring is tight and not shorting, as electrical resistance creates heat.
• Factory Reset and Re-sync: A firmware glitch can occasionally cause the sensor to hang on a specific value. Perform a factory reset by holding the reset button (or following the software reset path in Settings > Device Options > Reset). Re-add the device to the Alexa app to ensure you have the latest firmware version, which often includes sensor accuracy patches.
• Relocate the Device: If the thermostat is installed near a heat source (like a lamp, kitchen appliance, or in direct sunlight), no amount of calibration will fix the issue because the heat is localized. Move the thermostat at least 5 feet away from any heat-generating electronics or direct sunlight.

Heads Up

• Avoid Over-Calibration: Do not calibrate the device by more than 10 degrees. If you have to offset it by more than 10, the sensor is likely defective or the environment is too extreme, and the device should be replaced under warranty.
• Wait for Thermal Equilibrium: Always wait at least 20 minutes after installing or removing the faceplate before trusting a temperature reading; the act of touching the device transfers body heat to the sensor.
• Check for Dust: Use a can of compressed air to gently blow out the vents on the side and bottom of the thermostat housing. Dust buildup can trap heat inside the chassis, leading to artificially high readings.
• Verify HVAC Cycle: Ensure your HVAC system isn't "short-cycling." If the furnace kicks on and off rapidly, the heat from the vents may be hitting the thermostat prematurely, causing it to read 72°F and shut off before the rest of the room actually reaches that temperature.