If your device is displaying this icon for any of your sensors, this means you have a fair signal connection between that sensor and the HUB.
A fair signal status means that the sensor is functioning at a 60%-80% signal capacity. This could be the result of a couple of different things.
The sensor battery is dying.
SmartAC.com sensors are designed to only use special high-capacity AA lithium batteries that can operate in a wide temperature range.
Please ensure you replace all of your sensor batteries at the same time.
In the future you will have the ability to easily purchase high quality OEM replacement batteries at discounted member pricing.
The sensor is too far from the hub, this issue can be solved by moving the hub closer to your sensor.