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2006 C230 sport
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Discussion Starter #1
In my 2006 C203 Sport, when climate control is set in AUTO, temperature sets at somewhere between 64F-68F (the dial is just out of the left most position), AC ON, hot air goes out for about 5-10 minutes occationally, making the cabin feels very hot.

I have reset the climate control unit by the dealer (don't know how they do) and by myself by holding the two most left keys together and let the two leds blinking for a while. But it does not help. Outside temp. sensor seems reading the correct temperature reading in all the case.

I have checked on the two interior temperature sensor, one on the climate control unit and one on top, and they both drawing airs into itself and seems OK. AC function is OK because I can feel cool air comes out if I set the temperature dial to the left most clicking position. AC light is always ON when the problem happens.

Is there any information that can help me to check what is wrong?
 

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2006 C230 sport
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Discussion Starter #2
Is it possible to be caused by the dew point measured by the humidity and dew point sensor is not right, so the climate control tries to defrost the windshield when it sees the dew point is too high (humidity too high)?
 

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'07 C280 4matic, '06 530i, '98 ML320
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cabin temp sensor may be giving wrong values... just a thought.
 

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2006 C230 sport
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Discussion Starter #4
I have tested the system response from the cabin temp. sensor by heating the sensor erea up by a hair dryer (both the sensor inside the CC panel and the one on the overhead control console). I did not see any response from them at all. In another words, even I heat up the air around them a lot, the air duct still blowing hot air out. However, I am not sure the cotrol rules embedded the controller, so there maybe a huge delay/time constant applied. Also, the air temperature out from the duct may not be related to the cabin temperature alone, I guess.

The strange thing is that at the first 10-20 minutes after I adjust the temperature, or from the car started, the temperature control seems OK to blow air out in right speed and temperature, but it will blow hot (not the hottest, but definitly hotter than the set temperature) in high speed after this period, no matter what the temperture setting is.

I am out of warranty. The Dealer I visited said they did not find out anything wrong on the sensors and the controller by a quick test. I am not sure how detail their test is. I am going back to them tomorrow.
 

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2006 C230 sport
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45 Posts
Discussion Starter #5
Dealer said they cannot see anything wrong from the Star-Diagnosis when performing a check. They suggest me to wait until the situation becomes worse. Any suggestion.
 

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2006 C230 sport
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Discussion Starter #6
To my surprise, I just found out that indeed there is no humidity dew point sensor installed in my car:confused:! --- After removing the cabin air filter, I can see there is only a seat for the humidity dew point filter on the side wall of the cabin air intake box (the rounded piece in blue in the picture).

I don't know someone worked on the car took it, or it is not needed for a C230 with non-digital climate control. Can someone owns a 2006 or 2007 C230 confirms if his/her car has the sensor?

The part number of the sensor is 211-830-05-72, according to WIS. It should be attached to the seat shown here.
 

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climate control is out of regulation

Hi zhuorongdeng,
Did you fix this problem on your car?
Sometime my climate control is out of regulation, blows very hot air and very cold air alternatively. (2006 C203). Not all the time though.
 

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Coupe/Convertible Forums Moderator
CURRENT: 2011 SL550, 2011 C300 FORMER: ML350, CLK550 Cabriolet, C240, ML320, 300TD
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19,447 Posts
A lot of cooling problems are related to low refrigerant. Often times, you'll get cold air on one side but not the other or wave of cold and hot air. My advice is to check that first.
 

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2006 C280 4Matic
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Over the last couple of months my 06 C280 4Matic has developed the same thing, that is, that at the first 10-20 minutes after the car is running the temperature control (auto/AC) seems OK it blows air out in right speed and temperature, but it as if it has a mind of it's own, it will suddenly blow hot (not the hottest, but definitly hotter than the set temperature) in high speed after this period, no matter what the temperture setting is. Does anyone have suggestions?
 

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Coupe/Convertible Forums Moderator
CURRENT: 2011 SL550, 2011 C300 FORMER: ML350, CLK550 Cabriolet, C240, ML320, 300TD
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It may be a bad cabin temperature sensor. There are two - one on the A/C control panel, and another on the overhead console. You could try blowing compressed air in them to see if there are any obstructions. Otherwise, you may need to get diagnostics run with SDS.
 

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1966 230SL, 2006 C230
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147 Posts
I have this issue now in my 2006 C230 Sport. Blows hot air out defrost and floor regardless of ACC temp setting, except for Max Cool which blows ice cold air out dash vents. I take it off auto and vent position control and fan speed control work as expected, but temp control does nothing - hot air only.

I'll look for a humidity sensor.

My dealer did the vent position reset and can't figure out the problem. Makes sense to me that it is a cabin temp sensor and the car thinks it's ice cold in the cabin. How do I confirm this? Is it only through codes or what?
 

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CURRENT: 2011 SL550, 2011 C300 FORMER: ML350, CLK550 Cabriolet, C240, ML320, 300TD
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Pulling codes from the ACC would give you the correct answer.
 

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1966 230SL, 2006 C230
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Pulling codes from the ACC would give you the correct answer.
Dealership says there are no codes.

It seems that if there are no codes, the dealership's robot mechanics stop working on the problem. That leaves owners working together on sites like this. I expect more than I get from dealerships, and I ususally get more from the user community that I expect.
 

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CURRENT: 2011 SL550, 2011 C300 FORMER: ML350, CLK550 Cabriolet, C240, ML320, 300TD
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If there are no codes, then SDS still has diagnostic steps that can be followed. For example, they can check the input values of the temperature and humidity sensors, actuate the ventilation system dampers, etc. These steps are all there in SDS on a button that says "Troubleshoot by means of complaints or symptoms" and the "complaints about functions but not fault codes". This puts the tech into a series of test steps that can lead to finding the problem, but of course the tech has to (a) know how to use this tool and (b) be willing to do this diagnostic work. Unfortunately, too many shops hire "robots".
 
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