What Does a Blinking Light on a Motherboard Mean?

By Thomas McNish

Motherboards are sometimes colloquially referred to as "mobos."
i Comstock/Comstock/Getty Images

Just as all roads lead to Rome, all devices on a computer lead to a motherboard. But while all motherboards have this fact in common, they can also differ greatly. Each motherboard has different specifications, depending on the manufacturer, the size of the motherboard and its physical configuration. Because of this fact, a blinking light on a motherboard can potentially mean different things.

Power Supply

Every computer has a power supply, which takes AC power from the wall and converts it to the DC power used by the computer. The power supply, like most things on a computer, is connected to the motherboard. In some motherboards, such as the ones found in many Dell computers, a blinking light on the motherboard indicates a bad power supply. If your computer won't fire up, but you notice a blinking light on the motherboard, chances are you've got a bad power supply. Before buying a replacement power supply, take its form factor (such as ATX or BTX) into consideration, as well as its wattage and physical dimensions.


Another possible cause for a blinking light on your motherboard may be bad RAM. Your RAM may be corrupt, or possibly even seated improperly (not pushed firmly and securely into its slot on the motherboard). Another possibility is that you added the wrong kind of RAM when you installed a different stick. For instance, if your motherboard takes SIMM (single inline memory module) RAM, and you purchased a DIMM (dual inline memory module) card, then it either won't fit properly or won't be recognized by your motherboard. If, however, you've never replaced or added RAM, then this isn't likely to be your problem.

Front USB

Many computer towers have USB ports located in both the fronts and backs of the cases. Because the USB ports on the front get used more frequently than the ones in the back (due to external devices being pulled in and out of the ports more frequently), they run a higher risk of becoming damaged. In some cases, a damaged front USB port can cause a blinking light on a motherboard and may even prevent your computer from starting up. To fix this problem, you can simply disconnect the cable that connects the front USB to the motherboard. Start the computer up again, with the front USB disconnected, to see if the light is still blinking.

Getting Specific Answers

Because each motherboard is different, different codes mean different things. For instance, if your Hewlett-Packard laptop won't start and emits three beeps when you try to power it on, this will mean something different than a Dell that gives you the same signal. The only way to know exactly what's causing your motherboard to blink is to look in the owner's manual. There should be a list of error codes in there. If not, you may be able to find them online. However, if you still can't find answers, you can always contact a computer repair shop for answers. Tell the tech about your problem, as well as all troubleshooting solutions you've attempted.