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2004 CLK55 (A209)
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Discussion Starter #1
Hi all,

I know this has been covered a lot of times and i have found a lot of threads regarding it but im hoping someone can clear a few things up for me.

My A/C doesn't work and the code reader is telling me the foot well and filter flap is blocked. From what i can gather the A/C wont switch on if the control module has a fault on it to protect it. These are on my fix list for the winter.

The problem at the moment is the car blows hot air even when on cold so i went out and bought the 10k thermistor as said in the other threads. I have removed the OCP but there doesnt seem to be a small fan with a thermisor on it like in the thread. Is there anything in the OCP that needs changing? I can solder no problem but a picture of what to change would help.

The ACC has a small fan in it as ive had that apart to clean all the dust out. Is there a thermistor on this fan as i cant remember it. Does anything else need changing to fix this problem while I have the car in bits.

I have a 2004 Convertible.

Thanks
 

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CURRENT: 2011 SL550, 2011 C300 FORMER: ML350, CLK550 Cabriolet, C240, ML320, 300TD
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I believe that even if a damper flap is malfunctioning, the ACC system should work, though you may get no airflow, or air that is the wrong temperature. Here's a good thread about the thermistor:

 

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2004 CLK55 (A209)
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Discussion Starter #3
Thanks for the reply rudeney. Thats the thread I had a look at and got the thermistor from. When I opened the OCP last night I was looking for the fan shown in the pictures but there isnt one in there. It was mainly switches, IC's and a large silver round thing. As i couldnt get the cover all the way off (map reading lights stopping it) I couldnt see what it was but definately no fan.

Does the facelift model have a different OCP, or maybe the European version is different to the US.
 

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You have to disassemble the OCP to access the thermistor and the fan - it's on the underside of the circuit board. I checked EPC, and there are only two differences in the CP for a CLK55 - TeleAid or not and Sound System (i.e. Bose audio) or not. That is regardless of country
 

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2004 CLK55 (A209)
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Discussion Starter #5
I stripped the unit so I could see both sides of the circuit board but sure I couldn’t see a fan. I’ll have another look tomorrow and take some pictures.

What exactly does the OCP control? It has 8 connectors going to it and in my iCarSoft it has its own menu so it must be more than a light dome.

It has a circular unit in it which twists and comes out. It has to speaker on it so i assume this is the mic for the phone. I don’t have an SOS button though. The car does have the Bose system.

is it possible the pre-face lift only has a thermistor in the ACC and this does the control regardless of roof up or down? Could this have been an extra feature added to the face lift models? I will also check the part number on the unit as perhaps someone changed it for a coupe one in the past.
 

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2006 CLK 350 Convertible
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619 Posts
Here is what the circuit board looks like. The fan and the thermistor are in the upper right corner - black with white spot in center.
 

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2004 CLK55 (A209)
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16 Posts
Discussion Starter #7
Well the good news is im not going nuts. Defiantely no fan on my board. There are 4 holes which i assume are for the retaining clips of the fan to go into but no fan.

Ill strip the ACC this weekend and have a look if the fan on that board has a thermistor.

Am i right in thinking then that there is only one control regardless of the roof up or down? The part number is correct for my car as I checked the EPC.
IMG_2654.JPG
IMG_2656.JPG
IMG_2661.JPG
 

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Very strange! Did this problem just start happening, or has it been this way since you owner the car? And did you just recently acquire it? The reason I ask is because I am wondering if the previous owner had an issue with that fan not shutting off and draining the battery (a not uncommon problem) so he removed it.
 

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2004 CLK55 (A209)
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Discussion Starter #9
Its always been like it. I bought the car in April this year and we had a good summer so it being my weekend car I always had the roof down. The A/C never worked so I took it to be regassed and they said there were no leaks but the clutch wasnt coming in on the compressor. I then discovered that it wont work if there are errors on the A/C control module. They did a pressure check and it was ok.

There are a lot of problems with the heating and cooling system. I have a iCarSoft Pro so I read out B1590 (A32m2 Charcoal flap) and B15A8 (M2/15 (Left and right footwell flaps). I found the M2/15 code strange as it has dual control so it should have the seperate motors M2/10 and M2/11. At the moment the air always comes out of the footwell regardless of the control setting. It is now telling me the refrigarant level is too low.

I ran live data on the ACC and it said the humidty was 58% and air temperature was 77 (25 celcius). Now i was in my garage and the outside air temp was only 12 celcius so theres something up there which is why I had a look on forum and heard about the thermistor.

Theres so much wrong at the moment I dont know where to start. At least its not stopping me driving it though. I plan during my time off at christmas to strip the dash and have a look at the stepper motors.

The circuit board looked clean (no solder or flux) so if it had been removed it was a good job. Wouldnt this through an error code on the OCP though if it was just removed? There were a lot of recieipts with the car and a lot of work was done by an independant but couldnt find anything related to this, thats not to say it didnt happen though.

All I need to do now is find a diagram for A 209 820 10 01 to see if a fan is supposed to be fitted. Cant see it being an easy task so if anyone on here has the A 209 820 10 01 – Sound System with Tel and wants to have a look it will be appreciated. Cant find one on eBay either so could try contacting Hella.
 

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I did a quick eBay search and found this (no recommendation for or against that seller - just the first one I found):

https://ebay.us/V5EHOS

But I see that you are in the UK, so shipping may be an issue. Note that shows a different part and it's for a coupe, but I believe only the housing is different - the internal circuit board is the same. Worst case you would need to swap just the thermistor/fan.
 

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2004 CLK55 (A209)
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Discussion Starter #11
Thanks for the link rudeney, I’ll see if they will ship internationally.

I just got home and tried the built in diagnostics, press and hold REST. Sensor 1 and 2 which are internal and external are both showing 12 which seems right to me as the car is in my garage with the roof down and the outside temperature is 12. This tells me the thermistor is OK and the car is monitoring temperature correctly despite not having the OCP thermistor. It must be using the ACC one regardless of roof up or down. The Freon pressure was reading 0 though.
Looks like I’m going to have to fix the stepper motors to clear the faults and take it to an air con specialist.
 
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