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Smell...

7K views 16 replies 14 participants last post by  jbanks15 
#1 ·
My 2012 SLK250 (R172) has an odd smell from the AC system...I wouldn't say it was a bad smell...or a good one, just one I'd like to eliminate if possible.

I searched this site and saw some references related to R171s having a "crayon" smell...and I guess it could be described as that?

Anyway...I couldn't find anything on this subject related to R172s...so has anyone else any experience with this ? Where is the cabin air filter located ? Where is the air intake located ? Any other ideas/tips ?

Thanks
 
#2 ·
#3 ·
The r172 cabin filter is the same as the r171's and in the same location.
It's slightly easier to install on the r172 as the cover has a couple of tabs on one side that makes aligning it with the rest of the holder easier on installation.
 
#4 ·
I have has a similar experience in a few air conditioned cars over the years, and each time this smell was detected it was a sign that the air con gas pressure needed topping up, the second sign would be the chilled air would be be less chilled and the smell increased as the
system became less effective, the crayon smell is the first sign.
 
#5 ·
I've had my car for almost 30 months and for the first 18 or so I would only occasionally get the 'crayon' smell when the top was up - not sure if it was A/C related though, because when the top is up, the A/C is generally on. I do notice that when the A/C is on, it seems to work really well, though. Like you, the smell didn't really bother me but was noticeable because it was 'different'. In the last 12 months or so, I don't recall getting the smell - maybe I got used to it or maybe it has faded with time? Or maybe it's just because for the past several months I've been able to drive top down much more often. With winter setting in, the top will be mostly up and if it's there, I should notice it.
 
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#6 ·
Hi, yes, I too have this exact same waxy smell in my 2013 SLK250. I've done a few car bomb odor eliminator sprays with the AC on and the heating on, which helps for a short time, then the smell returns. Changing the cabin air filter next. Then will do another deoderizer can in the car. I've heard you can also put those charcoal pouches in your car to absorb weird odors. If all this fails, I'm going to take to an auto place and get an industrial ozone machine clean inside the car. I can't bear the wet/waxy smell!
 
#7 ·
I had a 2006 SLK55 that I purchased used. I live in South Florida. I smelled that "burnt crayon" smell right away. The car was still under warranty so I took it into the dealership. they completely went over the interior and eventually changed out the carpet and padding. Nothing helped. They finally came to the conclution that it could be the underlying foam core behind the bumper. That was not changed but within a year after I bought the car, I sold it to a person living in the Northern states. He did not complain about that shell.
I do not think that smell actually is from the air conditioner as stated in other posts. My reason for saying this is I actually felt the smell became stronger with the air off and windows partially opened.
As a funny side note, several months after I sold the SLK, we went out to dinner with friends who owned a C class Mercedes. They picked up and as we got into their car, my wife and I looked at each other. Yes you guessed it, their car had the SAME SMELL!
 
#8 ·
smell

If you will refer to my post from the past 6 years and/or do a search for "crayon smell" you will see what was determined to be the cause of this smell. It is the rustproofing material used in the frame and on some cars I am assuming it is leaking out and producing this smell. I bought a 2010 with less than 500 miles and it had this smell. After 2 years of trying to rid this car of this smell MB gave me a 2012 and it has the same problem but not nearly as bad as the 2010. Just learn to live with it, you WON'T get rid of it unless you get rid of the car. Just my 2 cents.
 
#9 ·
If none of the above, It could be worth taking the lid off the box that contains the battery as this is where air is drawn from outside into the heating/aircon system. Could be something in there like a dead crayon....... worth a sniff.

6 months ago my battery box was full of rain water as the battery box drainpipe had blocked, causing all sorts of smells in the car.
 
#10 ·
Thought I would add my two cents. I worked as an engineer in car battery manufacturing plants for 10 years. We recently picked up a 2015 SLK350 and I immediately noticed the odor in the car, which I would characterize as a sulfuric acid smell vs burnt crayon, but they are similar. When you walk around a warehouse with 100,000 batteries on charge you get to know the smell pretty well.

After reading above I checked out the intake box and has been mentioned there sits the battery right in the fresh air intake box! Not the best location. AGM batteries are still a lead acid battery and are vented and will release some sulfuric acid fumes, no way around this. I did see the vent tube running down next to the drain and not sure how far that tube runs, but it should run as far as possible outside the fresh air intake box. Will explore this next time I am under the hood.
 
#11 ·
Every time I get the rushing scent of fresh crayons in the air, I always get that great feeling of being reassured of the fact that Jezebel will never ever have any rust problems:laugh:. This is the rust proofing wax on your vehicles folks. Have a look in your door jambs and all over the chassis and you will see that off white/yellowish substance used in all the seams and welds. This is not AC related, just temperature related. You cannot get rid of it, it is just going to be there and the smell will come and go based on the temperature (the warmer the more noticeable):wink:.
 
#15 ·
Pretty much gone until you roll the windows or put the top down eh? I would imagine the charcoal in the filter absorbs the odor to the point it does become very noticeable in the ventilation system after time. I just changed mine recently and although the smell in the interior is not as noticeable with the interior sealed up, it is still there when the top is down or the windows down, provided it is warm out.
 
#14 ·
Interesting!
Just 2 weeks ago I bought my 2001 320 SLK with 8K on the clock and the next day walking into the garage noticed a different smell. Sounds like what everyone is talking about. Now that the wax rust proofing was mentioned, I do recall that smell from the rust proofing bay next to me when I worked for a Ford dealer.
Over the years I've noticed that certain cars have a particular scent, like VW Beetles. They apparently had horse hair in the seat padding.
 
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