Question GPU Red Flash

[Keplerm13]

I am currently in the process of case swapping. I only have my gpu, mobo, and cpu plugged in with power. I wanted to test to see if it would boot. When I turned on the computer the gpu just flashes red for a second and then stops. I unplugged my gpu power cables and this still happened. I checked all cables to make sure they are plugged in all the way and this still happened.

 

[rgd1101]

full system spec?

 

[Keplerm13]

i5 8400k
evga 1080
650w evga psu
16 go ddr4 ram 3600
1 tb hardrive and 250 gb ssd