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2006 Mercedes ML 350
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68 Posts
Discussion Starter #1 (Edited)
I bought a 2006 ML350 about 4 weeks ago and have a question about the rear A/C system. The ML has the dual zone climate system. On the right control I know that pushing the rear button will turn the red light out and the rear system comes on and the auto button in the rear lights up, and you have rear air flow. I usually want the rear system on to put a little air in the back of the car on the really hot days we are having. Sometimes I noticed that the rear air was off and the red light would be on at the rear switch on the front control unit. I was blaming my wife for hitting the switch in the rear with her purse when she gets in the car. You can push the switch and the unit comes back on and all is well. My question is now the rear button is off by default every time you get into the car and start it up. you can pust the button and the red light goes out and all is well until you park the vehicle and restart it again. I thought once you turn on the rear air it would always come on each time you start the car. The owners manual does not say if you have to push the button on each startup. The only info they give is when it is real hot you should shut the rear system off to allow max cooling in the front area. Does the system not come on at startup due to high temp outside or do I have a problem with something . It just started or I just noticed yeaserday having to turn it back on each time. I hope some one can tell me if the red light is on by default when you start the car in the morning. If you turn it on and shut the car off it will come back on if you just restart the car. Could I be having a voltage problem or memory problem with one of the systems? That is the only setting on the vehicle that is not working the way it was.
 

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2019 X350d, 2017 GLE500e, 2012 ML350BT (sold), 2013 A200 Exclusive(sold), 2009 ML350CDI(sold)
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250 Posts
I am not answering your question. But I have tried figuring it out many a time. We have now found the solution.

We have ordered the W166 with Thermatic rather than Termotronic.

Our kids don't mind. They have horns and four legs, so they only travel in the trailer.
 

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2008 ML320CDI Iridium Silver/Black, NAV, P2 pkg, Sirius, Harmon Kardon. Active Bi-Xenon
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478 Posts
I just noticed on mine defaulted to the rear being off (red light on) after sitting in the hot sun for a good part of the day. However, on most days when I start the car the rear system is on (red light out) just the way I left it.. I am guessing the system is programmed to allow maximum cooling to the front seats based on inside and ambient temp.
 

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ML550, W212 E350 4 matic, 1966 Corvette C2 convt.
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2,675 Posts
I have noticed that when I had my 06 ML500 and with my current 10 ML550 the rear off light is on when the outside ambient temps are very high. I can over ride this by pushing the rear off button to allow cool air to the rear. If I do not manually over ride the off it will revert back to the normal on position when the cabin cools down. I believe its doing that to cool down the front where most of the occupants usually sit. Think its perfectly normal
 

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2006 Mercedes ML 350
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68 Posts
Discussion Starter #5
Thank you for checking your rear a/c system. I looked in the owners manual and even searched TSB's on Alldata to see if it was a problem that everyone was having. I did find some info in the owners manual that stated for best cooling on extreme hot days to turn the rear off so that the front area would cool faster. After a few days of 100 degree heat it cooled off for a couple of days, and the rear a/c started working the way I thought it should. The Benz was smarter than I am, it knew what it was doing all along!! I just did not want to have a problem that the dealer would have to fix. The defroster went out on my 04 ML and it cost about $1,000 to repair. I hope the 06 does not have the same problem in the future.
 

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ML350 2007
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2 Posts
Back flap is off by default when you start car after long stop so it starts pumping air at full throttle to make drivers zone temperature comfortable first. When it achieved it releases back flap and now air flows to the back.
 

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2006 Mercedes ML 350
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68 Posts
Discussion Starter #7
Thank you for the info on how the rear a/c air flow works. It would of been nice if the owners manual explained how it was designed to work. I guess I was expecting problems after having a problem with my older ML's rear air system. I hoped this newer ML did not have the same problem. Anyway all is well and it works fine.
 
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