Green light on motherboard is flashing
Usually indicates a power short, or power fluctuation on one of the components. If you still have the board manual, check it for information, usually under "troubleshooting" or similar.
> First, check the power supply. This is important. If you don't have a tester, gotta' swap with a good one.
> Check your memory; have you been digging around in the case recently, possibly accidentally bent something that is touching something else, etc.?
> As Madman suggested above, clean the dust out of it. I do not think that is the problem, but in theory excessive amounts of dust might cause a short. Not likely, but at this point try everything. I usually use a small vacuum cleaner with the vent reversed to "blow" and a crevice tool; it's a great way clean it out. Of course, do this on the rear porch, you will be amazed at the cloud of dust coming out of it.
> Unplug and re-plug all components, including memory, video cards, any other components.
> If no joy, then remove all components and do a bench build; use one stick memory, no OS drive, mouse, keyboard, power supply and monitor only connected. Make sure the board is sitting on a piece of cardboard or foam, and cross the two power on contacts. If it still does the same thing, sounds like your motherboard failed. Bench Build
[EDIT: additional detail]: When you power up, you should get the POST screen coming from the BIOS on the monitor.
Edited by ranchhand_, 13 March 2018 - 06:03 PM.