Hello everyone.
I'm new to this forum site.
I have a wd hdd model:WD500AACS SATA.
the Problem is that this hard disk is sometime detecting and some times not.
Some Time Motor spin and some time even if the motor spin it doesnt detected.
Is The Problem is with PCB or some where else .
Pls Help Mekk
Thank You all.

Hi Ansarisuhail,
Based on your post this might be because of bad connections, or maybe bad sectors, or even corrupted data that messes the partition information. My suggestion to you:
1) try to connect using different sata ports, different cables and try to connect to a different system if possible.
2) try running the DLG software, to repair any potential issues with the HDD itself. You can look at the link below on how to use it:
http://wdc.custhelp.com/app/answers/detail/a_id/940 .
3)If the hard drive is damaged then you can check the warranty from the following link and send it for RMA,if its under warranty
http://support.wdc.com/warranty/index.asp?wdc_lang=en

Try conections as Lincon say

If this not work and your data is important, better contact with local pro

Probably bad heads, maybe bad fw too or maybe bad platters too