Q: The a.c. unit will not turn on

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The a.c. won't come on at all. The indicator lights are out or off and if you open the good there seems to be air blowing underneath

My car has 66000 miles.
My car has an automatic transmission.

While it is not unusual for the climate control unit to fail in Mercedes models, the most likely culprit is a system pressure issue. Either one of the pressure sensors in the A/C system may be bad, or the system may have a leak and actually be low on refrigerant or even empty. The A/C system has its own set of diagnostic codes, so you may want to have a service professional diagnose the A/C system before replacing random parts, as they can be quite expensive.

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