C36 AMG, C43 AMG (W202) 1995 - 2000

Climate Control Mixer

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Old 11-13-2013, 01:45 PM
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98 C43
Climate Control Mixer

I noticed that when I increase the temperature from cold to hot, it either takes a very long time for the temp to switch, or it doesn't do it at all. The climate control unit appears to be working fine, visually. Is this an issue with a mixer?
Old 05-28-2014, 02:29 PM
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Anyone? More specifically, the car will go to HOT and COLD, but doesn't seem to like anything in between. AC works fine too. I cleaned out the Duovalve to no avail. Any help would be greatly appreciated.
Old 05-29-2014, 02:21 PM
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Did you check/replace the interior thermometer? I've noticed that with mine too. I always just assumed it was the way the climate control worked vs. normal AC. If I lower the temp a bit it will do so gradually, and if I want cold air to start blasting I have to drop the temp by like 10 degrees
Old 05-29-2014, 02:23 PM
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Originally Posted by nd4spd13
Did you check/replace the interior thermometer? I've noticed that with mine too. I always just assumed it was the way the climate control worked vs. normal AC. If I lower the temp a bit it will do so gradually, and if I want cold air to start blasting I have to drop the temp by like 10 degrees
Thanks. How do you know if the interior thermometer is bad, and where is it? I recall running the diagnostic and the module didn't flag any errors.
Old 05-29-2014, 02:29 PM
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I imagine an error would come up if it was really fried, but after 16 years it can get full of dust and stuff. They're pretty cheap from what I remember, so I just replaced mine when I got it.

It's located under the black plastic bit where the dome lamps and sunroof button are. If you pull down that whole thing it's a little black cube in the top. You can locate it from the vents on the bottom side of the plastic
Old 05-29-2014, 02:32 PM
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Originally Posted by nd4spd13
I imagine an error would come up if it was really fried, but after 16 years it can get full of dust and stuff. They're pretty cheap from what I remember, so I just replaced mine when I got it.

It's located under the black plastic bit where the dome lamps and sunroof button are. If you pull down that whole thing it's a little black cube in the top. You can locate it from the vents on the bottom side of the plastic
Good point... So you think this is the culprit? In order for me to get heat, I need to go max, and it gets real hot, but there is no real "in between" or "warm" air I can achieve.
Old 05-29-2014, 02:39 PM
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Originally Posted by akimoto168
Good point... So you think this is the culprit? In order for me to get heat, I need to go max, and it gets real hot, but there is no real "in between" or "warm" air I can achieve.
Not sure. As I said mine seems to act similarly and I thought it's just normal. If you raise the temp by a few degrees does it eventually raise??
If the display doesn't have any errors, the temp sensor is the only other thing I could think of.
Old 05-29-2014, 04:46 PM
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1999 C43 AMG, 2005 E55 Wagon
Sampler blower motor, mounted by dome light

http://www.partsgeek.com/catalog/199...wer_motor.html
Old 05-29-2014, 08:52 PM
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Originally Posted by Sulaco
Sampler blower motor, mounted by dome light

http://www.partsgeek.com/catalog/199...wer_motor.html
If it is this temp sensor, then why does manual adjustments not work? For instance, if I am on EC and manual (not climate control), then shouldn't I be able to control the varying degrees of warmth? I can suspect this temp sensor if I was in auto mode, but my issue is even in manual mode.
Old 05-29-2014, 09:46 PM
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beats me, that was my only guess
Old 05-30-2014, 01:52 PM
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Originally Posted by akimoto168
If it is this temp sensor, then why does manual adjustments not work? For instance, if I am on EC and manual (not climate control), then shouldn't I be able to control the varying degrees of warmth? I can suspect this temp sensor if I was in auto mode, but my issue is even in manual mode.
Perhaps, but doesn't the manual mode only really control the fan? The temperature would still be relative to the temp inside the car. If it's not the temp sensor it sounds like a faulty control unit could be the culprit.
Old 05-30-2014, 04:01 PM
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Originally Posted by nd4spd13
Perhaps, but doesn't the manual mode only really control the fan? The temperature would still be relative to the temp inside the car. If it's not the temp sensor it sounds like a faulty control unit could be the culprit.
what he said.

a faulty sampler blower motor or CCU is almost certainly it. more than likely the sampler blower motor. it's the cheapest, easiest thing to replace, too.

if your sensor is blown then it doesn't matter what fan speed you set it to. if it thinks it's 100 degrees in the car at all times, then it will only blow cool air unless you set it to HI on the temp setting.

if it thinks it's always 35 degrees in the car, it will always only blow HOT air unless you set the temp setting to LO

So, go all the way to the top and bottom temperature settings and see if it switches from hot to cold. I recommend starting with LO. If you start with HI it can take some time for the system to blow cool air because of how hot the heater core gets.
Old 06-06-2014, 01:45 AM
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Thumbs up

Originally Posted by Sulaco
what he said.

a faulty sampler blower motor or CCU is almost certainly it. more than likely the sampler blower motor. it's the cheapest, easiest thing to replace, too.

if your sensor is blown then it doesn't matter what fan speed you set it to. if it thinks it's 100 degrees in the car at all times, then it will only blow cool air unless you set it to HI on the temp setting.

if it thinks it's always 35 degrees in the car, it will always only blow HOT air unless you set the temp setting to LO

So, go all the way to the top and bottom temperature settings and see if it switches from hot to cold. I recommend starting with LO. If you start with HI it can take some time for the system to blow cool air because of how hot the heater core gets.
Good point. Thanks for contributing
Old 06-06-2014, 01:48 AM
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Actually, I was envisioning a mixer, like what is found in many imports. For example, if I set it at 72F, doesn't it just allow x-amount of coolant and fresh air to formulate this temp, regardless of a reference point (ie. sampler blower motor)??
Old 03-21-2015, 11:16 PM
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Just an update to this issue. I've changed out the duo valve, but the same issue is here. I can get the air either cold or HOT. There is no in between. If I set at 75F, it's the same as 50F, to get any heat, it needs to be set at HI. This is manual mode, not using AUTO. What else can it be? Sampler motor? I just don't see how a sampler motor matters because I am manually telling the car to output 75F. If I was doing climate control, then I can see the sampler motor playing a role. Stumped...

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