Thermatic A/C

survey

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I need some help with regard to climate control and A/C. My 2008 C class has 2 Zone Thermatic controls. Pushing the Auto button seems to cool the car and maintain the required temperatures. This despite the fact that the A/C light may not illuminated. However one cannot set air distribution to any symbol. If I press the A/C button,then I have access to the distribution symbols. Which of these or both are climate control?

Can someone enlighten me as to whether the cooling is indeed operating without the A/C light illuminated? Also with the A/C light illuminated will the compressor indeed be switching in and out as required by the temperatures set?

I have some some time just pressed the A/C button (red light ON) and left the cooling to get on with it assuming that the compressor is switching out when temperature is reached.
 

television

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EC lamp lit is air con off on most of them
 
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survey

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EC lamp lit is air con off on most of them

Certainly in my handbook it says 'switch on the air conditioning with air dehumidification function. The indicator lamp in the A/C button comes on'

It must take a certain individual to write the handbook to make it capable of more than one interpretation!
 

television

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We had a big post on this issue a few days ago and I could be wrong,,just turn the controls to min temp and try it both ways,,you will soon see the difference
 
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survey

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Turning the temps to low, it appaers on mine anyway that with the A/C light off and Auto on the cooling works. Similarly with the auto off and the A/C button lit, the cooling works.

If this is indeed how it should work, reading the manual it appears that the A/C lit means that there is a dehumidification function as well as the cooling. By deduction this means the Auto thermatic cools but does not have a dehumidifying function. I thought that all A/C had a dehumidifying effect?

And leading on from that does the compressor cut out when the cooled set temperature is reached under both settings? Looking at the rev counter I cannot see movement either way?
 

keith100

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Hi Survey

On my 204 with the 2 zone systeme, the a/c light is on all the time, summer or winter (unless I turn it, or the whole system, off).

I can access the dist. setting or fan speed in two ways.

I. Push the auto button off and the pics for the settings and fan speed show up. The system is now set on manual.

2. Push the dist button only and the auto light goes out and the setting pic appears. If I push the fan speed buttons only, the auto light still goes out and the fan pic appears.

No matter what I choose, the a/c light stays on. One odd thing - if I turn the a/c button to off, I still I get cold air, whether its in auto or manual. Hmm... whats it doing? Perhaps it only turns off the drying function in winter?

I have a Canadian version and I understand these systems do differ around the world - even the US system is a little different to ours, but I hope this helps

Cheers

Keith
 

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204's are different to 203's ......... (I've had both) .......... on auto, in the 204 ......... you cannot set the direction of the air .it does it automatically.

If you switch to manual ..... when the red light is on ........the aircon is on !!
(which is totally opposite to a 203)
 
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survey

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So guys. Logically with the Auto button pressed and the red auto light lit, the car is cooling to whatever temperature has been set but the distribution is automatic with no manual override, whether the A/C button is illuminated or not. With the A/C button pressed and thus red light lit, cooling is also working but has a dehumidifying function and gives one manual control of air distribution.

Am I now correct on this?

I always thought that with any A/C there is always a dehumidifying function so how can the AUTO setting not give a dehumidifying function as it must be using the A/C compressor to operate its cooling?
 

Hertfordshire Merx

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On all late Mercedes models and including the 204, when the AUTO button is pressed and the red light is illuminated, it will endeavour to reach the temperature position you have dialled in on the temperature setting. For prior knowledge and as a matter of fact, I would not go with the temperature setting as being totally accurate, and furthermore as mentioned you will lose the manual ability to set the direction of airflow.

There are reasons for this. When the AUTO button is depressed other components in the climate control system take over to make the system as fully automatic as the button suggests to make your driving more comfortable and safe. Applicable models are fitted with cabin temperature sensor(s) dependant on dual or even tri zone (S Class 221) systems to measure the temperature at various parts of the vehicle. Solar sensors will pick up the direction of UV light, so if a vehicle is partially parked or travelling in the sun the temperature will adjust accordingly.
 
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survey

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Hertfordshire Merx - but does the A/C button have to be lit as well if the Auto button is set and red lit? Or will the Auto switch in the A/C without the A/C button being lit
 

Hertfordshire Merx

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When the auto button is lit the control unit will energise the air conditioning compressor as and when required on the information that you set the temperature at and what the sensors are picking up.
 
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survey

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Hertofordshire Merx - cheers for your prompt response. So the A/C light does not need to be on when Auto is selected.
Perhaps someone can explain why the handbook only mentions dehumidifying with the A/C button pressed & lit and doesn't mention it at all when just Auto is pressed and lit. I had always understood that climate control that operates the compressor provides a dehumidifying operation as a consequence of cooling and this Auto or A/C should have this effect??
 


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