Where is the low pressure valve on my C220 Mercedes?

[prasad]

Where is the low pressure valve on my C220 Mercedes, i want to recharge the AC unit.

[kaamran]

If it is to recharge the AC unit then it is located in the engine compartment, go to the driver side left front bottom

on receiver-drier is the low pressure switch is located there where the charge coupler is near to this

[prasad]

the AC now is not cooling at all. What should i be doing.