When I press the power button, all of the fans—including the case fans and CPU cooler—spin briefly and then stop. The RAM lighting remains on, but the system does not appear to complete POST, and the motherboard's diagnostic LEDs do not light up. This started after the PC was affected by a blackout. I have been using an AVR since I built it. My system has a Ryzen 7 5800X3D, RX 9070 XT, MSI B550 Tomahawk Max WiFi, 32GB of DDR4-3600 memory, and a Seasonic GX-850 850W power supply. What should I check first?
1 Answer
Because every fan stops and the system does not reach POST, this sounds more like a power or motherboard protection issue than a normal fan-control setting. Turn the PSU off, unplug the PC, disconnect the AVR, and hold the power button for several seconds. Then clear the CMOS according to the motherboard manual and try booting with only the motherboard, CPU and cooler, one RAM stick, and the power supply connected. Reseat the 24-pin motherboard cable, CPU EPS cable, graphics-card power cables, and RAM. Also check that the CPU cooler is connected to the CPU_FAN header. If it still shuts off immediately, test with another known-good PSU if possible; the blackout may have damaged the PSU or motherboard even if the RAM LEDs still receive standby power.
It is all of the fans—the case fans and the CPU cooler. I suspect it is failing before POST because none of the motherboard’s diagnostic LEDs come on when I press the power button.