Some PS4 users' consoles have a blinking red light on the hardware, indicating the PS4 is overheating.
Named the "red line/light of death" as a callback to the Xbox 360's "red ring of death," since the launch of the PS4, some users have reported their PS4s powering off after the console flashes a red light on top of the console. Multiple YouTube videos have shown the same occurrence: the red line flashing and three beeps sounding before the PS4 turns itself off.
According to the PS4's user guide, the red light appears when the PS4 is overheating. The guide advises leaving the system off for a while. If the problem persists, there may be something wrong with the hardware that can't fix itself with a simple reboot. NeoGAF user Inner-G wrote his PS4 got the "red line of death" from overheating because the fans never turned on. He posted a video documenting the problem. Shown in the video, he turns on the PS4, the system checks its storage status and restarts, and after reaching the "Welcome Back to PlayStation" screen, the blue light on the system turns red, the console beeps, and shuts down. Back in October when Yoshida was asked about the "red line of death," he said it was "not true."
Several pre-launch systems, such as ones received through a Taco Bell promotion and ones provided to journalists, had problems and had to be sent back to Sony. Sony Worldwide Studios President Shuhei Yoshida said Sony was aware of "isolated incidents" of PS4 incidents. A Sony representative estimated about 0.4% of pre-launch PS4s had technical issues and said this number was within the company's expectations for an at-launch product. Beyond the "red line of death," users have also had problems of their PS4 systems not responding, and Sony has created a forum for troubleshooting. The pulsing blue light problem seems to be different from the overheating issue of the blinking red light.
While the "red light of death" appears to be an overheating issue rather than permanent brick, if the fans never turn on and if leaving the console alone for a while does not cool down the system, the system most likely cannot be saved.