Pressure switch power steering

[Cvija]

Hi,
Can anyone tell me how to check my connector for pressure switch on power steering? How many volts should be when car is running or something like that so I can check it that everything is ok?
Also, does anyone know oem number for pressure switch?
Is it possible that whining sound that comes from PAS is due to bad and leaky pressure switch? Because I don't know what is role of pressure switch in system, can someone explain me please...

Cheers

 

[JamesBryan]

It's only really there to raise the revs at low speed/idle.

Whining noise is just the pump, they all do it but if it's particularly loud it'll be on its way out. Check your fluid level.