The d2 Thunderbolt 3 may show a red solid light or a red flashing light at times. This may signal that the device is above temperature specifications or that the fan has failed, but more than likely it’s a false indication of fan failure. Some early d2 Thunderbolt 3 devices had an issue where the device would falsely report a fan failure which would cause the red light to come on even though there wasn’t a real fault with the drive or fan.
If you experience a red light on your d2 Thunderbolt 3, please do the following:
Check for a possible temperature problem by seeing if the device is hot to the touch
Ensure that the fan on the back of the unit isn’t blocked
For Windows computers, you may also download SeaTools for Windows and use the “Drive Information” feature to check the temperature of the drive. The maximum temperature is 70 degrees Celsius, but it’s best to avoid operating at sustained temperatures above 60 degrees.