mercedes/e-class/2010-2016

A/C power not coming on.

Hello, when I press the A/C button to put it on, the red light just blinks once and then goes off. The fan blows out only air that is not cold. Please can someone tell me what the problem might be before i take it to a mechanic? I do not want to be cheated. My car is a 2011 year w212 E300. Thank you in advance.

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