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Discussion Starter #1
Hi all,

I own an E320 and had a question about using the heater. This is how I turn on the heat on the driver’s side:

1) I turn the temperature knob to the right (clockwise ) ---> No. 1 from the picture

2) Then I press the Auto button ---> No. 14

Now my question is if the AC off button (No. 8) is not activated, will the AC be on as well and use up more gas?

The reason I am asking is by default whenever I hit the “increase the airflow” button (No. 3) or the “Automatic air distribution and airflow button” (No. 14), the AC off is inactivated.

Thanks in advance
 

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2017 Police Interceptor Utility, 2017 Police Interceptor Sedan
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The AC will come on only when needed, so no, under most cold conditions the AC will not come on, except very occasionally to assist with dehumidification (like for defrosting). The impact on fuel consumption is negligble.
 

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Discussion Starter #3
Thanks flyboyike, but if I decided not to use the Auto setting and turn on the heater manually, should I press on the "Increase the airflow" button and then press the AC off?
 

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Try to trust MB engineers?
My wife likes to play with clima controls as well and I know it is annoying for few seconds at the end of heating cycle, but when stabilized the system in Auto works perfect for me.
I use AC a lot in California and never could notice any change in mpg. Actually winter (usually 50F) produces lower mpg, what I blame on longer warm up and additional rain resistance.
 

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Discussion Starter #5
Kajtek,

I really trust MB engineering! But am just curious to see if i decided to use the heater manually and would not like to use any AC, ca i turn the AC off button? Is that the right way to use the heater?
 

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You might try to see if how it works for you.
I keep AC on in my car for 2 reasons
1. AC compressor need exercise from time to time and computer takes care about it.
2. quite often when driving in the humid weather with heat on, the windshield gets foggy. The MB clima takes care about it .. .if the AC is on. Driving Ford I am pretty annoyed that I have to make constant manual adjustments.
 

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You might try to see if how it works for you.
I keep AC on in my car for 2 reasons
1. AC compressor need exercise from time to time and computer takes care about it.
2. quite often when driving in the humid weather with heat on, the windshield gets foggy. The MB clima takes care about it .. .if the AC is on. Driving Ford I am pretty annoyed that I have to make constant manual adjustments.
Correct, except that on a new car like a W211 the AC compressor runs always (no clutch), it is just turned to the minimum volume when AC is switched off (I think 3%). The compressor then gets exercised irrespectively of the ACoff button.

Kajtek,
I really trust MB engineering! But am just curious to see if i decided to use the heater manually and would not like to use any AC, ca i turn the AC off button? Is that the right way to use the heater?
I'm confused about your approach, what do you actually want to operate manually? You cannot operate heating manually, you can only set the preferred temperature and the car tries to reach that automatically even if you put "Auto" to off or ACoff to active (AC OFF).

You can switch HVAC fan speed to manual and you can switch air flow direction to manual but you cannot adjust heating power manually (that is: adjusting the air flow flaps between cold and heater air). Of course the AC compressor can also be switched off (functionally, not "physically" off), I think you are more after consequences from turning AC off.

If you wanted to, you could switch AC off at cold temperatures if cooling is not needed and if you face no problems with humidity (moisture condensing on glasses etc.). But you would not gain a lot because the compressor is not running at full power even at auto (although I think US cars are coded differently, Euro cars cool the intake air only sufficiently to keep relative humidity low enough while US cars at least used to have a coding that makes the car cool the air down to the maximum and then warm it up, but even here the difference is not significant if outside temperature is not high).
 

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Kajtek,

I really trust MB engineering! But am just curious to see if i decided to use the heater manually and would not like to use any AC, ca i turn the AC off button? Is that the right way to use the heater?
The "correct" way to use the climate control system is to set the desired temp and press auto.
 

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Discussion Starter #9
Thanks Diesel Benz and flyboyike,

Yes, I used to just set the temp. and use the Auto option and let it does its job, but then someone who doesn't own a MB said if the AC button is on you will be using up the gas...

Diesel Benz,
I was after what you said: "you can only set the preferred temperature and the car tries to reach that automatically even if you put "Auto" to off or ACoff to active (AC OFF)" since "cooling is not needed and if you face no problems with humidity" but now I know I won't gain alot...

So I understand there are two ways to operate the heat:

1) "The "correct" way to use the climate control system is to set the desired temp and press auto."

2) Use the Auto button and activate the ACoff button

3) Use the airflow buttons and activate the ACoff button ---> Which is what i am doing after that someone commented on the mpg.

And I understand now that the first two methods burn almost the same amount of gas...

Thanks again for all your helpful replies.
 
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