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Hi everyone. I have a 2007 CLK 350 convertible, and my climate control is acting up. Unless one or both temperature controls are set on LO, the system blows very hot air. The AC also works when the convertible top is down. From what I've been able to tell, these symptoms indicate that the thermistor in the overhead console is bad or the wire has come loose, causing the system to think it's zero degress inside. I'm adventurous enough to replace of resolder the thermistor, but can't figure out how to remove the overhead console to get there. I've removed the front lens and pulled the white tabs forward, as indicated for the hardtop and sunroof models, but the console still doesn't want to budge on my convertible. Any ideas? Many thanks, Dan
 

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Welcome to the 209 forum. As you have not completed your profile, we do not know your location, which is unfortunate.

The climate control systems fitted in some markets (Europe) have a diagnostic facility that can display the outputs of several important a/c temperature/pressure sensors to help fault finding.

Ref your OCP, did you remove the 2 screws showm on the WIS document below.
 

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Thanks, Keyhole. I didn't know about the two screws. I'll try that tomorrow. Location is Florida. Just updated my profile. I appreciate your quick reply! Best, Dan
 

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Dan, did you ever fix the heating/ac controls, and if so how? I am having the exact same problem on my 2006. Works fine with the top down!
 

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Ray, Not yet. I successfully removed and reinstalled the overhead console yesterday. However, I will have to wait on a new thermistor, which I also ordered yesterday. When I separated the circuit board from the rest of the assembly, I found that the existing thermistor had a broken lead. Unfortunately, the break was so close to the body of the thermistor that I could not repair it by soldering. When I get the new thermistor recommended by another poster (http://www.benzworld.org/forums/w220-s-class/1460424-need-help-c-diag-4.html), which I hope will be next weekend, I'll try again. I'll repost then. Take care, Dan
 

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It Worked!

Looks like success. The whole process took about 45 minutes. Toughest part, actually, was disconnecting the modular connectors from the overhead console. The existing thermistor was fried right at the body (see photo OC3). I removed it from the fan (see photo OC2), soldered the new thermistor in its place (see photo OC3), and reassembled everything. Once done, somehow everything miraculously worked again. I wish the best to others on this repair, and would be happy to stay tuned to answer any questions that might help. Take care, Dan
 

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Nice job, Dan!

I can't figure out how to remove the panel over the top (under the convertible top). I am afraid to pry it off and don't see any screws.

How do I take that panel off? Once I do I can see if I have the same thing going wrong w/ my ac/heat.

Thanks!
 

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Ray, I used a flathead screwdriver, and inserted it between to plastic trim panel and the top of the interior edge of the windshield to gently pop the connectors off. There are about five or six snap connectors to hold it in, and once I got started, they seemed to pop pretty easily (not nearly as hard as some interior door snap connectors I have dealt with). The long, narrow piece of plastic will then slide out rear-wise and expose the top of the console. You'll see two phillips-head screws that hold the entire unit. Once you've remove the screws, you can push both holding clips in slightly, and the whole unit will swing forward and drop out. I found that using a flat-head screwdriver, using a twisting motion, helped remove several of the wire connectors. Good luck! Dan
 

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Thank you! I'll give it a try when the weather improves here in MI.

Ray, I used a flathead screwdriver, and inserted it between to plastic trim panel and the top of the interior edge of the windshield to gently pop the connectors off. There are about five or six snap connectors to hold it in, and once I got started, they seemed to pop pretty easily (not nearly as hard as some interior door snap connectors I have dealt with). The long, narrow piece of plastic will then slide out rear-wise and expose the top of the console. You'll see two phillips-head screws that hold the entire unit. Once you've remove the screws, you can push both holding clips in slightly, and the whole unit will swing forward and drop out. I found that using a flat-head screwdriver, using a twisting motion, helped remove several of the wire connectors. Good luck! Dan
 

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Have done this fix and it works now can control heating in my CLK was an easy fix really, thanks for the pics and details.
 

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Looks like success. The whole process took about 45 minutes. Toughest part, actually, was disconnecting the modular connectors from the overhead console. The existing thermistor was fried right at the body (see photo OC3). I removed it from the fan (see photo OC2), soldered the new thermistor in its place (see photo OC3), and reassembled everything. Once done, somehow everything miraculously worked again. I wish the best to others on this repair, and would be happy to stay tuned to answer any questions that might help. Take care, Dan
Dan, I am about to embark on the same adventure here. I finally got the connectors off which i agree seems like the hardest part. Anyhow, can you confirm if you used a 10K thermistor?
 

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I never got around to trying this fix yet. But I'm wondering if there is another way to do it w/o replacing the thermistor. With the top down, both thermistors are disabled and the system works great (both temperature knobs work). Is there an easy way of disabling the system by just cutting a wire or some easy fix like that? How does the system get disabled w/ the top down?
 

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The ACC knows to disregard the sensors via a CAN bus signal from the soft top controller. There would be no easy way to emulate that. I guess you could try removing the thermistor to see if the system would ignore it. But in doing that, your just a couple of solders and a $0.15 part away from fixing it.
 

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The ACC knows to disregard the sensors via a CAN bus signal from the soft top controller. There would be no easy way to emulate that. I guess you could try removing the thermistor to see if the system would ignore it. But in doing that, your just a couple of solders and a $0.15 part away from fixing it.


Thanks! I guess I'll try to get in there and see if the thermistor is damaged, hopefully before winter gets here!
 

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Semi success

I did the the thermistor replacement and the AC now seems to be working properly. That's the good news. One thing though, is the fan is not super quiet anymore. I think the bearing or the blades may have moved a tad during the uninstall / install operation. There is now a slight "whirring" noise. Ambient sound tends to drain it while driving, but it's there when getting in and out of the cabin...
 

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I got around to doing this repair yesterday. It worked! Thanks so much Dan for posting pics, or I wouldn't have known where to solder the new thermistor. The old one only had the "head" of it left, and it was loose in the binnacle.

Whole job took about 1 1/4 hours, but that included a drive to the hardware store - make sure you have a #6 Torx bit before you start - it's necessary to separate a rear cover off of the pc board.

So it all works, and I would have had no idea how to fix this w/o this board!

I brought it in to the dealer about a year ago, and their diagnostics pointed to the unit in the dashboard, which would have been $800 and would have fixed NOTHING. Whenever I pointed out that the system worked w/ the top down (told them 3 times), it was pretty much ignored LOL
 
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