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2002 ML320
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Discussion Starter #1
The weather here has gotten warmer and with that I have a new issue...

Normally when I would start the car in warm (hot) weather 80°+ the recirculate function comes on for a bit to aid in cooling the interior... then turns off and allows fresh air to come thru.

The issue now is that in 80°+ weather the Recirculate will not turn off... unless I turn the car off and start it again... then it will turn off only if it feels like it...

I do not want to freeze my compressor by leaving the recirc stuck ON...

Is there anything you guys can think of that causes this? Will it be expensive to fix? Are the recirc parts easy to get to without removing the entire dash?? (Removing the dash and the expense behind that is what concerns me)

TIA to the extensive knowledge base here!!
 

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1998 c230 170K
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Do you have the digital or knob controls for the CCU? I went through a similiar problem a while back, my vacuum element dried out. There is a vacuum block underneath the inside passenger side (at least on mine) that has all the element hoses connect to there, check for loose connectors or hoses.
If you have the digital have a look at the link
http://www.benzworld.org/forums/w202-c-class/1372302-ac.html
Is there any hissing sound under the dash area>?
There is a motor that actuates the element (s) with a delicate plastic arm that can strip. I really hope its not that. B
 

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Discussion Starter #3 (Edited)
I have the manual CC system...

I have no hissing sounds... BUT... normally I hear a slight clicking/thumping from the passengers side of the car when everything is working normally... could be a vacuum issue that is causing a flap to open and close repeatedly. When the car is stuck in Recirc, I do not hear that noise. Could it be that element failing/failed?

Addition: Can I disconnect this flap from the vacuum system and just have it open (fresh air) all the time? I rarely use the recirc function anyway. Just until I can get the dash removed and attack the issue head on.
 

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From what you have mentioned so far yes, it does sound like the vacuum element is bust. If you want I can post what had to be replaced on my 98' a few years back.
I did not replace myself, as you probably know if this is the case the dash needs pulled.
If you indeed do need to do this and want to DIY I have a tutrorial also.
Couple of things to try out since you unfortunately don't have the digital CCU.
From a dead stop with the CCU on re-circ. accelerate quickly, if you hear that thump or thunk I think that would verify a leaking vacuum element. Even thought the vac block supplies vac pressure a sudden vac demand will give a temporary reduction in sys. vacuum. I know you don't want to do this but if you were to put the heat on does the heat function well?
To answer your last Q, If you can find the hose nip on the block underneath the passenger side and plug it off you can give that a try. You'll have to find a rubber cap to put on the outlet that will fit tight or else you will have a hiss going on. B
 

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Discussion Starter #5
Definitely... if you could post what had to be done to yours that would be fantastic!!

Who did yours for you? Dealer or indy? What was the cost to do this?

Yes, heat works fine... A/C works fine... just no fresh air and I am afraid to keep it on too long in recirc mode... a friend froze his A/C compressor on his Honda from keeping the system in recirc a lot.
 

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Discussion Starter #6
My other question would be... why does this issue get exacerbated when it's warm out?

Also I am going to try your test suggestion... and I think that when it is in Recirc mode (button pressed, light on when its working properly) that the thumping noise does go away.

Does the vacuum hold the flap in "fresh" mode then?
 

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Its close to 2k unless DIY

Here is the bill, Dealer did the job. I did not have the time to do the pulling of the dash myself. Many of the trim pieces are expensive and I certainly did not have the correct pulling tools at the time, so..
Honestly I hope its something other than that element but...It might be worth the inspection fee you might luck out and have it be something else.
Some of the climate controls have gone bad lately as well. I am somewhat lucky that I have a digital CCU other than they do blacken after a while. I with postpone my CCU DIY since Metafly beat me to that. B
 

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Discussion Starter #9
Wow... thanks for the info guys! I have to really get myself revved up for this either way I go about it... I will definitely have it diagnosed before going further.
 

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Edit: Take it back, after looking at your invoice, you had a total system overhaul, down to the heater core.
Here is the bill, Dealer did the job. I did not have the time to do the pulling of the dash myself. Many of the trim pieces are expensive and I certainly did not have the correct pulling tools at the time, so..
Honestly I hope its something other than that element but...It might be worth the inspection fee you might luck out and have it be something else.
Some of the climate controls have gone bad lately as well. I am somewhat lucky that I have a digital CCU other than they do blacken after a while. I with postpone my CCU DIY since Metafly beat me to that. B
That linky I posted covers a how to on Bmeister's described element issue. That problem looks relatively doable. The DIY'er's problem (ultimately) was with the bellows - which required the complete removal of the dash. He also lists all of the tools required along with a pretty complete diagnostic of the area if you haven't had a chance to check it out.

After reading his symptoms, I am afraid I will have the brutal task of tackling dash removal at some point. Please keep us posted.
 

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Discussion Starter #11
So... will I still need to take out the dash to get to the problem area in my car or will it be accessible thru the glove box? Since I am not having to replace anything like heater core or the flaps themselves?
 

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If its actually the element its the whole thing. There is simply no access to the effected part without removal. The element mount and re-attaching the arm to the vent flap.
Before proceeding I recommend a basic estimate done to verify. B
 

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Discussion Starter #13
Damn... lol... I was hoping for a different answer... I do have the car in Saturday and will have them diagnose the issue then.

Thanks again!
 

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B knows a lot more about this stuff than I do, but according to the write-up I posted, if it is just the element itself and not any of the tubes leading into the dash, it can be replaced without removing the dash from my understanding.
 

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Discussion Starter #15
Maybe there is a difference in the face-lifted W202's where they moved it... I dunno
 
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