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.


The reason why your AC button only flashes the red light means that a fault code is stored in the Air Conditioner control unit. What you need to do is read the fault codes from the AC control unit. In some cases the fault code can be something ridiculus such as immplausiblity of temperature sensor or low battery voltage. Those things can prevent the system from operating.

One other thing that you can and should check is the freon level. Get a A/C recharge kit that comes with a gague. Start the car. Connect the gauge to the low pressure AC port. Read the pressure on the low side of the A/C. If you have freon leak, it will prevent the AC system from operating / blowing cold air.

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