AC blows cold and hot at same time..
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Newbie
Joined: Mar 2010
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2000 S430
AC blows cold and hot at same time..
I've read all the posts I could find about this issue. My '00 S430 just started this bizarre function. Cold on driver, hot on passenger. I use the Rest - Charcoal filter procedure and got code 1271. The Bus isn't communicating with a stepping motor (does anyone know where these components are located in the car?) The problem is I don't know what to do with this info..?? I used the air direction push buttons procedure to reset it, but that didn't do anything as far as solving my problem
More info: the AC usually works perfect when I first crank and take off. After some period (10-45 min no set time period), the passenger is getting hot air. I turn off the automatic controls on the control panel and the center vent, then back to Auto, and voila, I USUALLY have cold air blowing from both sides of center vent. But, this fix is usually temporary and has to be repeated. Another weird result is that when I restore the passenger center vent to cool, the right vent at door and the rear vent blow hot. But not always. I just don't know what to do at this point. I wish there was some components(s) I could replace to fix it. No clue where to start. Can anyone help me or do I need to find a MB AC guru?
More info: the AC usually works perfect when I first crank and take off. After some period (10-45 min no set time period), the passenger is getting hot air. I turn off the automatic controls on the control panel and the center vent, then back to Auto, and voila, I USUALLY have cold air blowing from both sides of center vent. But, this fix is usually temporary and has to be repeated. Another weird result is that when I restore the passenger center vent to cool, the right vent at door and the rear vent blow hot. But not always. I just don't know what to do at this point. I wish there was some components(s) I could replace to fix it. No clue where to start. Can anyone help me or do I need to find a MB AC guru?
Last edited by ayersl; May 13, 2014 at 06:56 PM.
MBWorld Fanatic!
Joined: Jun 2002
Posts: 1,284
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From: North Carolina
2003 S500 - Toyota Corolla (in the rain)
Could possibly be your heater core sensors. Try swapping them around (or get someone to do it) and see if the problem moves from side to the other.
Super Member
Joined: Sep 2012
Posts: 690
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From: Montreal, Quebec
2009 E350 4M Avantgarde;mistress 2002 S600; wife 2014 C300 4M
blowing hot on one side and cold on the other side - I would look at the duo valve first, because it is supposed to shut off the hot water to the respective side.
There are may other possibilities, but I would eliminate the duo valve first.
There are may other possibilities, but I would eliminate the duo valve first.
Thread Starter
Newbie
Joined: Mar 2010
Posts: 6
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2000 S430
AC multiple personality
Thank you both for the advice! I will research swapping heater core sensors to see if it's something I could handle or whether I need a professional. Any direction as to where to find out how would be appreciated!
As to the duo valve, that has always sounded like a logical explanation, but where to find it and what to do when I uncover it is a mystery. Any ideas as to location and test procedure?
Whereas I used to have all the work done by a local MB shop, I'm now semi retired and the 2000 model S430 isn't worth a lot of money. It's kind of a balancing act of how much $ do you put into it before you are throwing good money after bad? Knowing my usual mechanic, he would want to replace a bunch of costly components rather than take the time to isolate the problem and actually repair the offending part. I'm not even sure how well trained MB mechanics on these complex AC issues. I was amazed to discover the complexity of these systems of sensors and motorized dampers and such are. After researching my HVAC system, I'm amazed at how it's worked so well for all these years without failure!
As to the duo valve, that has always sounded like a logical explanation, but where to find it and what to do when I uncover it is a mystery. Any ideas as to location and test procedure?
Whereas I used to have all the work done by a local MB shop, I'm now semi retired and the 2000 model S430 isn't worth a lot of money. It's kind of a balancing act of how much $ do you put into it before you are throwing good money after bad? Knowing my usual mechanic, he would want to replace a bunch of costly components rather than take the time to isolate the problem and actually repair the offending part. I'm not even sure how well trained MB mechanics on these complex AC issues. I was amazed to discover the complexity of these systems of sensors and motorized dampers and such are. After researching my HVAC system, I'm amazed at how it's worked so well for all these years without failure!
Super Member
Joined: Sep 2012
Posts: 690
Likes: 76
From: Montreal, Quebec
2009 E350 4M Avantgarde;mistress 2002 S600; wife 2014 C300 4M
the duo valve is located in the engine compartment on the passenger side just below the air intake box for the heating/airconditioning .
It has a pump and two solenoids
I think you can actually find a video on youtube (just search there).
It has a pump and two solenoids
I think you can actually find a video on youtube (just search there).
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Joined: Dec 2012
Posts: 2,474
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From: Ball Ground, GA (N of Atlanta)
2003 S500 2007 GL450
Start by spending some time on the "sticky" threads at the top of this Forum.
After that, Google is your friend...
This is a Chinese site, but the HVAC manuals are in English.
http://wenku.baidu.com/view/b0f34432...b6f1a10fe.html
This site has about 1500 info links on the W220, including HVAC.
http://www.mbca.org/sites/default/fi...ART%20HERE.pdf
There is a huge amount of info on-line, and a couple of hours of reading will answer many questions.
After that, Google is your friend...
This is a Chinese site, but the HVAC manuals are in English.
http://wenku.baidu.com/view/b0f34432...b6f1a10fe.html
This site has about 1500 info links on the W220, including HVAC.
http://www.mbca.org/sites/default/fi...ART%20HERE.pdf
There is a huge amount of info on-line, and a couple of hours of reading will answer many questions.
