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94 S420 activated charcoal filter

15K views 37 replies 15 participants last post by  samosali 
#1 ·
My 94 S420 does not have the activated charcoal filter system. So do I only have 2 filters to replace? One over the blower motor and one in passenger side under dash. Or do I still have a regular type filter where the activated charcoal would be? I want to replace it if it is in there ,but I don't want to disassemble and not find a filter in there either. Thanks,Tom
 
#2 ·
Tom
All US 140 s had the three filter system unless you dont have the switch on the dash. the first filter resides in the HVAC housing and the windshield wiperpan and mechanism needs to come out.
There is a filter under the triangular cover at the base of the windshield, and the other filter is in the footwell upper screen on the passenger side.
 
#5 ·
The activated charcoal filter sits down inside the AC plenum, and requires the removal of the wiper blades motor and transmission, it is collapsed with a vacuum tool and pulled out. There is another filter on top of the lower motor, and one in the passenger footwell. The "activated" which supposedly gets rid of odors coming from the outside, was standard on the 500 and 600 and optional on the others. The switch is on the console, and part of the HVAC control on the newer style also times out.
 
#8 ·
#10 ·
Sometimes mold grows in the nooks and crannies of the air ducts and other places. When I first got my W140, it smelled like an old dog with the air on. I let the heater run full blast as hot as I could get it for a good long time to dry out the passages. I had to do this a few times. It eventually went away. If it's really bad, and you can't get it to stop, you may have to take it in for a treatment. A chemical can be sprayed into all the duscts, and down into the evaporator chamber to kill the mold. They then spray a sealer in there that is meant to prevent future mold growth. I'm told this treatment works, but you may have to do it every year or two.
 
#11 ·
You're good! The mech told me that the treatment would be the first option. The labor on changing the center charcoal filter is $240. I bought the filter from MBparts for $150, just in case. The smell is really bad with the re-circulation filter button on. I don't notice the smell in heat mode. The other 2 filters have been changed, but it still smells. It reminds me of the Seinfeld episode of the smelly car. I was thinking the smell was from the horse hair in the seats until I found the answer here!
If the treatment is more than $240, I'm going to have him change the filter and clean it too.
 
#15 · (Edited)
#17 · (Edited)
I dont think freon has an odor, and to drain the system to see if it has a leak does not make that much sense. If the system had a leak it would have quit producing any AC.
You probably have mold, and my service advisor suggested the "run the heater at full blast" when I inquired about the filter change, it went away.
As I stated before, there are three filters. The one in the passenger compartment footwell, The one on top of the blower motor (I have been told that there are two verisions of that) activated charcoal and not. There is also a filter buried in the heater plenum, on the cars so equipped, that requires the removal of the pan below the windshield, the removal of the windshield wiper motor and geartrain, that filter has a seal that needs to be collapsed with vacuum before it can be withdrawn or installed. The article I saw showed it to be at least a half day jobto do them all. The Filters 1408350147 (dust/charcoal fresh air filter), 1408350247 (recirculation filter), and 1408300018 (climate control active charcoal filter) These three filters should add up to somewhere around $ 6/700 for the genuine stuff.
 
#18 ·
I've changed all three filters with MB geniune, included the center filter ($330) that's under the wiper motor. No mold or mildew was noted on any of the filters or areas around the enclosure. I tried running the heater on full blast for several days. Driving around with the windows down. The mechanic returned my old central charcoal filter and it doesn't smell. He mentioned that the evaporator is directly in front of this filter. The evaporator has a design flaw that causes, eventually, a slow freon leak. The smell is similar to that of a wet dog. You mostly notice it when first entering the car and then again when the fans first turns on. I'm next going to try an anti-odor spray that the service tech mentioned too. It's a type of odor eliminator sold for primarily for smokers cars. If it's freon, it won't stop the smell. The mech thinks it's more likely to be the freon leaking.

The purpose of testing the freon is to check and see if any did leak out. As we know, it's a closed system and should always be full to work properly. The mech will then replace the freon and add a dye to see if the leak can be spotted. The mech commented that the evaporator is one of the W140 flaws. It was never intended to be replaced, thus it's a 22 hour job.

I do believe I'm screwed on this one.
 
#19 ·
The evaporator is truly a weak link, MB did mine and split the costs 50/50 I was still in it for about 3 grand. You cant belive the job, the entire dash comes out, find someone good. there are more hoses and wires than on the space shuttle. I hope it is something else, like maybe a dead mouse. I drove from Fla to Mass, and when I stopped the car a lizzard crawled out from under the hood,
 
#21 ·
The expensive center filter should last 80,000 miles.

Good news, maybe. The smell is lessening. I sprayed lysol in the recirc vent in the passenger footwell. The smell is only in the recirc vent! Has anyone tried an ozone machine? Do they work???
The rest of the car passes the snift test. The odor is very concentrated to the vent. The freon is fine.
 
#22 ·
I'm still having a tough time totally eliminating the odor when the a/c first turns on. The smell is like a dirty sock, but thankfully it only last a couple of seconds. I've changed both filters (piano and charcoal filter in center) and the recirc screen (filter) too. Does anyone have any ideas where the mold is growing! The mech said the evaporator looked clean on the side he could see. I only notice the odor when the system first comes on. Is there another filter somewhere??? Please help!
 
#23 ·
I have found that keeping the duct work dry is very important in preventing the A/C from getting bad breath. One thing I have always done, both on my R170-based Crossfire and my W140s, is to hit the REST button when I'm done driving the car. This runs the fan at low-speed for 20-30 minutes after the ignition is shut off and helps dry-up any residual moisture coming off the evaporator.
 
#24 ·
Perhaps the evaporater water drain tubes are plugged. I suspect I might have a problem on my car. Even after my car sat in the garage for two days a large amount of water came out when I moved it. I would have expected all of the water to drain right after it is parked.

Has anyone tried to clean the drain tubes from underneath? On the w126 the tubes are known to collapse.
 
#25 ·
I'll try the rest button. A clogged drain line is a possibility too. I've made an appointment at the dealer for Monday. I'm tired of the wife complaining that my cool car smells bad. I could hear the dealer's service tech grasping his hands in glee preparing for a major smackdown. At this point I don't care, it must be done.
 
#27 · (Edited)
Only a minor bit of disassembly is required: :eek:

 
#32 · (Edited)
No


Not feasible at a reasonable price.

What is feasible is to get the activated charcoal cabin filter in place of the regular filter. That's in place all the time and has a noticable effect. Just make sure you get one with lots of carbon on it. Just got a cheap Chinese one and its just looks like gray paper and its no good. I've not tried the WIX which can be had on flea bay for $24 (also a $35 one there). Meyle is like $75. They definitely help with the fumes. If something really bad is coming recirculate button is always a good option. Just read some general Amazon reviews on WIX and they sound really good. Fits some 97-99 models, but not mine so got the generic for $35 which looks like what I've had before that works.
 
#33 ·
Guys, couple questions, i hope someone has expert opinion:

1. Is there any reason to replace pollen($350) filter if evaporator is getting done?
2. Any place to buy one for $100-150?
3. Do i care about at all for any reason at all? Car is 1994, 51k is that filter still ok maybe? Should i simply delete it from the system?

My eveporator will be done anyway, so i need to decide either just leave it alone, or replace/delete. I have no clue (cannot find any logical way to determine course of action) :) please suggest!
 
#34 ·
i assume you mean charcoal filter under the windshield in the box?

it is about 400 eur. the filter above the blower is ca 100 eur (with charcoal).

The filter (also with charcoal) under the windshield can be replaced any time and from outside (no need to remove HVAC unit out of the car) according to my data. you need to create a vacuum on a certain place once the wiper system is out.

my opinion is that your filter is still very healthy. at least mine was 8 years ago at 280.000 km.
 
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