andrewt1993

When the light on the A/C button is on that means that it is for air conditioning right? And when the A/C light is off that is for heating right?

Also, how do I get air flow through the vents without having to turn on the air?

balticgreen

Whether the car is heating or cooling depends on the temperature you have set with the dials. The A/C button controls whether or not the compressor will run. Air will flow as long as you have not pressed the "OFF" button.

The easiest (and recommended, I believe) setting is to press the "AUTO" button, set your desired temperature with the dial(s), and let the car handle the rest.

mbzusr

Not a stupid question especially if I thought the same thing I normally set a temperature for both sides and use auto. However, when the car is heating, I can turn it off without impact as it settles my mind. Is the a/C light then an indicator of if the compressor is engaged and ready to run rather than currently running?

For the second question that I've also wondered, "vent only" mode. Nothing that I've found...

bytemaster0

The compressor will always run if A/C is enabled. This is useful in the case that you need heat, but need to dry the air, such as in conditions that cause your windows to fog. Moist, hot air inside and cold outside temperatures mean quick condensation/fogging of windows. Generally, I hit "Auto" and then manually turn off A/C. That way, temperature levels, level redirections, including a short burst of automatic window defogging and other aspects are automatically regulated without needing the compressor.

420tee

I haven't had a car of any make in years that had a vent position. Very annoying. Must be some stupid gumment rule that causes unnecessary A/C use.

mjhawkins2346

Hmm, what if you run the fan to zero? Does it close the vents or do you get a vent type airflow. I thought I did but I'll try it again.
The A/C is typically used to modify the heated air, usually cooling it a bit to get a more precise temperature control. If it isn't humid I frequently use Auto then hit the A/C button to kill the compressor. A habit from the old days when compressors took more power to run.

EmiG310

All I do is set the temperature, then press auto, then I press the A/C button. This turns off the AC, but leaves the blower motor on auto, and the car regulates the temperature, without using AC ("vent mode"). The other option is to go full manual, control the blower motor yourself with the +/- button, turn the a/c on or off by pressing the a/c button, and don't press the auto button. Auto can be used with or without the A/C. The fact that the A/C light is on on the button means the compressor is engaged. I do like that the A/C on the GLK doesn't seem as harsh as some other cars, but it definitely can be turned off as well, at least on my 2010.

NYCGLK

What he said. Put in auto and leave it there.
I have never touched the A/C button in 5 years.