Disk Activity LED blinking in 1 Long and 3 shorts pattern

[POWER_ID]

So in the last couple of month i notice my Disk Activity LED on my PC Case is always blinking even when there is 0% Activity on all my drive and its blinking in specific pattern 1 Long and 3 Shorts (SMART Test is not Running), 1 Long 3 shorts on Bios Beeps thing mean i have Faulty Ram and i have that problem couple of time, but I don't know what this mean on Disk Activity LED

The PC :
Asrock H61M-DGS (Cant Detect 2nd ram slot sometimes)

Intel i5-2400
2x Corsair ValueSelect 8GB (16GB Total)
MSI RX460 4GB OC Edition

WDC WD10EZEX (WD BLUE 1TB 7200RPM)
ST3500312CS (Seagate CCTV 500GB 5900RPM)

sorry for bad English, its my 4th language 

[StDragon]

Are you sure you connected the HDD LED cable to the correct two pins on the MB?

[POWER_ID]

Just now, StDragon said:

Are you sure you connected the HDD LED cable to the correct two pins on the MB?

yup, i already check that
its connected to HDLED

[POWER_ID]

oh im using DEV Windows 10 btw

[StDragon]

You might be able to narrow it down with the Resource Monitor from Task manager. From there, check Disk activity.

[POWER_ID]

5 hours ago, StDragon said:

You might be able to narrow it down with the Resource Monitor from Task manager. From there, check Disk activity.

So out of my curiosity i try to Test my memory, I'm using MemTest64.exe from TechPowerUp and when I start the test the blinking pattern stop
the test doesn't show any error after running for around 4 Hours on Max Settings...