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Need Help with A/C diag.

97K views 68 replies 42 participants last post by  Rahees w220 
#1 · (Edited)
I need help on AC, and I have search in this forum, but couldn't find answer. Thanks in advance. Here is the code on the AC (press and hold REST button for 5-10 seconds).

Car: 2004-S430 4matic
(car parks in sun/cloudy day ) about 95 degree F = 35.5C
NR.00 - 30.8C
NR.01 - 0C (In-car temperature sensor????) where is this locate at?
NR.02 - 35.5C
NR.03 - 8,3C
NR.04 - 7,1C
NR.05 - 2,5C
NR.06 - 69C
NR.07 - 13bar
NR.08 - 40C
NR.09 - 12.2K
NR.10 - 1.9V
NR.11 - 44%
NR.12 - 39% (Sun Sensor???)
NR.13 - 48%
Only thing i can see here is NR.01 always display 0 Celsius and NR.12 range from (20% - 110%).
Symtoms: The only way i can get cool air is that I have to turn to 'LO' for both driver & Pass side. The fan seems to blow cold air evenly for both side. If I set temp. to say 65F it only blow warm air. I would like to fix it myself, but I really need your help to determine the replacement part(s). is it NR.01 or NR.12?
If NR.01 is gone bad what is this part call (or part number)? how to remove it?

thank for all your help.:crybaby2:
 
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#4 ·
Thanks so much. I believe N70b1 is malfunction. I talked to MB Part Dept. (dealer) and was told that have to replace entire overhead console ($485). Does anyone know if that true? Is there a way to replace just N70b1?
Has anyone have experience replacing this overhead console?
Thanks for all your help.
 
#5 ·
Have you tried getting some canned air (computer duster) and spray it in there for about 5-10 seconds. Then see if the sensor works. sometimes they appear to be faulty but are just either dirty or dusty. I am not sure how to take off the console but I know it is a separate part so you should be able to get it.
I found a picture of the sensor:
 

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#7 ·
S430 A/C Dignosis

I have the same problem. On 'LO', it blows cool air, slight higher temp at 54 5it blows hot air. Could you please tell us how you fixed the problem, did you change the sensor or overhrsd console? My dealer quoting $1800 for changing O/H console, replacing a dryer and a hose? Is this sound right?
 
#8 ·
Detailed teardown shows problem

Ok I have this same problem on my new to me 2005 S500 4Matic so I decided to dig a little further and I believe I have discovered the problem. I am not sure how many photos I can attach so this will take a couple of posts.

The above post notes 2 possible inside temp probes. This discussion relates to the one in the overhead console. I can't say whether or not my 05 has a probe behind the dash control, but it clearly has one in the overhead console so that is what I have concentrated on. As you can see form the pictures the probe is behind the grill slots on the right side the left side has a fake grill for symmetry.

First, to get the overhead console down take the 2 dome covers off by prying from the rear. You will then see 4 steel clips that hold it in place. See the yellow arrows in the picture. Pry them towards the center of the unit and you should be able to pull it down slightly as you work around then right down when you release the last tab.


Next remove the wires. The two largest ones are locked in place by levers (yellow arrow). Press the tab and move the leavers down and the connection will come out easily. The other wire connectors are friction only.
 

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#13 ·
Ok I have this same problem on my new to me 2005 S500 4Matic so I decided to dig a little further and I believe I have discovered the problem. I am not sure how many photos I can attach so this will take a couple of posts.

The above post notes 2 possible inside temp probes. This discussion relates to the one in the overhead console. I can't say whether or not my 05 has a probe behind the dash control, but it clearly has one in the overhead console so that is what I have concentrated on. As you can see form the pictures the probe is behind the grill slots on the right side the left side has a fake grill for symmetry.

First, to get the overhead console down take the 2 dome covers off by prying from the rear. You will then see 4 steel clips that hold it in place. See the yellow arrows in the picture. Pry them towards the center of the unit and you should be able to pull it down slightly as you work around then right down when you release the last tab.


Next remove the wires. The two largest ones are locked in place by levers (yellow arrow). Press the tab and move the leavers down and the connection will come out easily. The other wire connectors are friction only.
How did you know which one it was? Since there are two sensors.

I have the same problem but not sure which one it is.
I did the 1/2 paper trick and it sucks the paper ok.
Air Diagnotics is reading 0 degrees also.

Thanks
 
#9 · (Edited)
Now, remove all the torx screws on the back cover and after removing the bulbs push the complete circuit board out of the housing.

As you can see the control panel is one circuit board that includes lighting control, sunroof control and the inside temperature sensor. The yellow arrow is pointing at the thermistor in the center of the mini fan. As a side point, you can check out the fan operation: after you have dropped the console but before you disconnect the wires, just turn the ignition to the on position and with a flashlight you can see the fan spinning in an opening at the end of the unit.

Now the interesting part. The fan shroud which is just clipped to the fan base is, by design, a little loose. Not really loose, but you can jiggle it a little bit with almost no force. The problem is, as you can see from the second photo, the thermistor is attached (wires melted in place) to the fan housing.

Before I could tell exactly how this was put together I pried the fan cover off the fan base, and could then see the broken wires leading to the thermistor. Had this been a good unit taking the fan cover off would have broken the leads. In my case however I am sure the leads were already broken.

In my opinion the leads could have broken from: 1. contact with the fan (they run right up beside it 2. fatigue from micro motion of the fan cover or 3. corrosion of the leads or a combination of the above.

This last point needs some explanation. After the fan cover was off, I was evaluating the broken leads and just simply touching the 1/2 inch stubs, (that were still soldered to the board) broke them further. Something has certainly made them very brittle and delicate. The last picture shows what remains of the leads at the base of the fan.

Although I have very little experience with fine soldering, I am going try to reuse the thermistor using some new leads. Failing that there must be a way to source a new thermistor. I’d be interested in any information anyone may have on thermistors. Are they all very unique or will any old computer fan thermistor probably work?

I’ll report back on my soldering job.

Thanks,

John
 

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#10 ·
Just a thing to possibly help on the thermistors, a place that does sell lots of different types of thermistors is Digikey. That is where I sourced them from while repairing my solar hot water system. The ones I used there was a 10kohm thermistor. Since you have a thermistor there, you could measure the resistance at some known temperatures and then find out the type of thermistor it is.

G.
 
#11 ·
SUCCESS

SUCCESS!

Soldered it back together and hooked it up without reassembling it just in case it didn't work, and low and behold NR.01 now reads 24.6 C instead of 0.

The soldering job could have been better but hey it works. I did hold the thermistor with a wet piece of paper towel just in case the solder heat might damage it.

I plan to run the new leads up the outside of the fan case (since there is no way to put it back like it was) and melt some grooves in the top near where the thermistor used to sit, so it should remain well within the fan's air stream.

So there you have it, a definite fix to the inside cabin temperature sensor.

John
 

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#17 ·
SUCCESS!

Soldered it back together and hooked it up without reassembling it just in case it didn't work, and low and behold NR.01 now reads 24.6 C instead of 0.

The soldering job could have been better but hey it works. I did hold the thermistor with a wet piece of paper towel just in case the solder heat might damage it.

I plan to run the new leads up the outside of the fan case (since there is no way to put it back like it was) and melt some grooves in the top near where the thermistor used to sit, so it should remain well within the fan's air stream.

So there you have it, a definite fix to the inside cabin temperature sensor.

John

THANKS!!!! i have a 2005 s55, same problem, and nr.01 was reading 0... Took apart the overhead console and one of the wires was broken. I actually just wrapped a thin piece of aluminum foil around the wire through the plastic housing since I didnt want to take it apart and its all fixed! You saved me $430 on a new console, thank you again!!! I now have auto air again, wow i didnt realize how much i missed that feature!!
 
#15 ·
Well, it looks like you have the answer on this, and I assume it was the overhead sensor. I don't know what the dash sensor does, or even if it's there on my 05.

I have not had a chance to source a new thermistor, but if anyone finds one hopefully they will report here.

John
 
#19 ·
Funny this should come up today as I just pulled my unit again as the thermistor leads broke again. This time right next to the electronic part. These leads have become very brittle. I am now having difficulty getting a good reading on the resistance of the thing since the leads are so short.

The reading I seem to be getting is 200 K ohms at 25 degrees C which is within the range of units that are available, (although finding someone that sells single units looks challenging). So if anyone has purchased a replacement let us know what you used. Or if anyone has the circuit board out and the thermistor is intact, please take a resistance reading and post your results. Since I only got 6 months life from the last repair, a new thermistor would seem to be the way to go for a longer term result.

As for the rattle issue I can't add much other than to say logically it must be the fan. Are you sure it's this unit, and not the one in the dash? I have a slight rattle from the one in the dash and will pull it at some point. This procedure has been discussed in another thread.
 
#20 ·
Buzzing noise from dash

I had a buzzing noise on the dash everytime I switched on the A/C. Finally (today) I decided to pull apart the Command unit, and took apart the bottom a/c section.

Once you take it out undo the two screw on either side of the wood trim. Then open up the plastic case by pushing in the little tabs and pulling out the tabs on the sides.

Once this is done, you'll see a circular tube on the right hand side (Right hand drive car, unsure if its the other way around in left hand drive) pull that off and you'll find a very thin small cable (temp sensor) I found that when switched on that the cable was actually rubbing off the fan. So I repositioned it so that the wires where no where near the fan.

I put it all back together, then just did a quick test to see if it make an annoying little noise. It's now gone jobs a goodun!

Hope this helps for other people! If I get the time I will upload some photos.

Nas
 
#23 ·
jwells my friend i want to say thank you for saving me £520. i had exactly the same issue on my 04 cl500 and your guide helped me fix it. i did how ever buy the another unit of a breakers for £38 which i shall be saving as back up. just in case you never know the future.
 
#24 ·
Sunroof switch!!

With your help I was able to fix the buzing noise from the upper fan. I noticed that one wire was missing 1/2" of conductor and that the fan had lint. Cleaned, solder a new contact, made sure the wires were out of the rotating fan and everything is fine. Pictures attached...

One problem... the sunroof used to open up with one touch and slide back normally. Now it needs several back inputs to open all the way back and the down function does not seem to work. Any ideas why? Thanks.
 

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#25 ·
you need to reset the auto sunroof.

Basically open it all the way by holding the button back. Once it reaches the end of its travel, continue to hold the button open for another 3 seconds or so.

Do the same while closing. May take a few tries, but this is the general procedure.
 
#26 ·
Thanks for the feedback, almmendes, and especially for the photos.

The closing problem you report has been successfully addressed by the procedure OliverK mentions. You can also refer to the W220 S-Class Encyclopedia for the "Resets" link.
 
#27 ·
Resistance

Has anyone ever came up with the resistance of the N70b1 sensor??
I've tried soldering mine and it broke right at the darn thermistor. I cannot get my meter to read anything on what is left sticking out. It may just be some of the coating that is sticking out...
 
#28 ·
What a great post! Thank you so much. I followed it step by step and it worked like a charm.
I learned to solder in the process too.
I used the existing thermistor, just added some wire and ran it over the top of the plastic.
I just bought the car, spent years on the Jaguar forums and they were a huge help, but this is one of the most useful posts ever.

Thanks again!
 
#29 ·
Great post! It worked flawlessly for me on my 2006 S430. I first tried to use an upper console from a 2002 S430 but it wasn't a match. The A/C was corrected but I got a "Light Sensor VISIT WORKSHOP" warning. I realized they weren't a match after looking at the circuit board with was completely different besides the thermistor. That's when I soldered my old thermistor and it was great. Thanks again for the great post!
 
#31 ·
Hi everyone, i just performed this fix.. i ordered 2 different thermistors since they aren't expensive and i didnt want to take this apart a few times.

1st thermistor from Newark.com looks like the original part, but kept the NR01 showing above 55C

Description: NTC THERMISTOR, 500 OHM; Thermistor Type:NTC; Resistance:500ohm; Thermistor Tolerance:-1% to +1%; Thermistor Case Style:Radial Leaded; No. of Pins:2; Leaded Process Compatible:Yes; R/T Curve:2; Series:C

Don't buy this part for this application

2nd thermistor from ebay

10 x 10K OHM NTC Thermistor 5mm - USA Seller - Free Shipping

Specification
B Constant 4050K
Resistance 10K OHM
Temperature -30°C to +125°C
Thermistor Type NTC Thermistor
Tolerance ±5%

this part is much larger than the original thermistor. but it works like a charm. had to wire external of the fan housing and allow for slack so the plastic housing fits properly.

I searched through many threads and didnt' get a definitive anwser before, so yes, please get the 10k OHM thermistor and it WILL work.

This is a great forum, and we all need to update our trial and error results (and failures)

Thanks everyone!
 
#32 ·
Jwell, you've saved me from having to hear any more complaints from my wife about the bi-polar temperatures coming out of each side. I baked while my wife froze. Our car would be comfortable when the temperature was set to 59 or 60 F. No other faults were present. When I took the overhead unit and disassembled to look at the Pabst fan with integrated thermistor, to my delight the wires were broken. It looked like someone may have tried to fix the problem before and the small ball of solder broke away.

A little surgery and the unit is as good as new. The auto temp control actually works. :thumbsup:
 

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