Make sure the computer and external hard drive are powered on. If your external drive's LED behavior has recently changed (and particularly if the drive is no longer detected or has changed the way it interacts with your computer), begin troubleshooting by following these steps: This article will provide numerous useful links for checking and troubleshooting this behavior. Troubleshooting and links for when the light or LED on your external drive is blinking.The behavior of the light (or LED) on your external drive can vary in meaning depending on the drive model.