What does "Auto" button do when you turn on your A/C or a Heat? Does it maintain a preset temperature and blows hot/cold air only when the temperature drops/rises?

Also, when I got in today and started to drive, my A/C was set to 74F and it started to blow like it was set to 85F and then after a while the air got cooler. And then when I turned it up by one degree, i.e. 75F it would start to blow hot air again and cool down after a bit. Has anyone experienced this before? (Temperature outside was 46F today, so it wasn't because of it was hot outside).

 

Sounds like it is working just as it is supposed to work.

Automatic means the system will control the cabin temperarure automatically to the set temperature. It will also change the fan speed as needed.

When you started to drive the cold car (46 F) and the temp setpoint was 74 F the system heated up the air coming out the vents to a higher temperature and I bet it was blowing quite strongly too. The bigger the temperature difference between the set point and actual the higher the fan speed and higher the air temperature coming out from vents (or cooler than setpoint in cooling mode).

And I think the system also reads the outside temperature so just one degree increase in setpoint with cold outside makes the system to make a strong initial step to make sure temperature does get higher quite quickly.

 

timurik, if yours is a 2013, go to page 143 of the owner's manual here:

http://www.mbusa.com/vcm/MB/DigitalA...edan_Wagon.pdf

 

Thank you for your responses.

So, there is a cabin temperature sensor somewhere? Do you know where it is located?

 

Assuming that was a microphone for phone system , a friend of mine said that was cabin temp sensor , so not the best shot but you get the picture
Please see the blue marked area at bottom of the right hand side to the image ,it's what you asked for

 

I think the air temperature sensor is where BenzV12 already indicated. It is actually an air intake for the sensor located somewhere deeper inside the system, i.e. a small air tube is used to pull air inside the system and the sensor is located inside this air tube.

The next question then is how the system sets the different zone temperatures. That I do not know as I have not been able to find another air temp sensor inlet on the passenger side.

I guess the system uses the driver's temp setting as a reference. This would be that the passenger zone (or the third zone) air vent output temperature is higher or lower than the driver's vents output by the amount the temperature setpoints between the zones differ.

Someone else may have a better explanation.

 

Thank you guys!

 

If the high blowing bothers you at start up, just turn off the AUTO and use the AC button, then use buttons to manually change the temperature or fan speed. Then when it settles down, push the AUTO button and should work normally.
BTW, it may say AC, but it controls the heat also.

 

Thank you.

But my concern was that when I was raising the temperature only by one degree from 73 to 74, the car would blow really hot air for say 20 seconds or so. And AUTO was not turned on.

 

If it was only for 20 seconds, sounds to me like it was just reacting to the change you made. However, someone else may know more about HVAC the M-B way than I do.