Mercedes-Benz Forum banner

1 - 8 of 8 Posts

·
Registered
1998 C280 - 400,000 miles
Joined
·
32 Posts
Discussion Starter #1 (Edited)
HELP! No air is coming out of dashboard center vent when AC is running. All other vents are working. Could this be a control problem or is it something in the mechanicals behind the dashboard?
 

·
Registered
1995 mercedes C220 base model
Joined
·
16 Posts
hello fatherfixit

solved this problem in my car last spring. While accelerating with A/C on the center vent would shloooop shut closed intermittently and open again while not accelerating. Eventually it would stay shut all the time with no air blowing out

Behind the dashboard are a series of rubber bellows/modules/diaphragms/elements that are controlled by engine vacuum + vacuum pump module in the car

These 'bellows' draw vacuum to move small levers that open/close the vents to your A/C system depending on where you have chosen the air to circulate. Over time some of these bellows develop leaks/tears around the edges of the rubber diaphragms resulting in vacuum loss and partial to complete failure of air flow paths to some of the vents in your car.

to fix this requires removal of the dashboard/center console to gain access to the bellows

these are very relevant videos to the problem you are facing in your car and have pretty detailed instructions/visuals on dashboard removal, explanation of how the system works and i would say are a must watch if you are just gonna dive into this.

dash removal
--------------------

climate control vacuum module replacement
--------------------

other posts on the forum related to your problem:
---------------------

defroster flap part # 2028000175 <------- THIS PART WAS THE FAILURE POINT THAT CAUSED MY CENTER VENTS TO REMAIN CLOSED
element.jpg


circled in this photo is the location of this vacuum element
IMG_20181016_122204.jpg



there may also be a change over block located under the hood of your car on the passenger side near the firewall/passenger side mirror. it is also a potential failure point causing the leak..... its a small rectangular block with a series of vacuum lines leading to it.... how ever I am not completely sure if this part is in your car given its a 1998.

vacuum change over block part # 1298001478
IMG_0168.jpg



also make sure the hoses aren't damaged or something as well and you reconnect the appropriate colored hose to where it belongs, it would be a shame to replace these vacuum elements and put everything together again only to find out the leak was actually somewhere else or something has been routed wrong
 

·
Registered
1998 C280 - 400,000 miles
Joined
·
32 Posts
Discussion Starter #3
quasi_mentos,

I appreciate you putting together all this information - it was very helpful. I watched all the videos and concluded that my problem is definitely in the ventilation system behind the dash. I've decided not to tackle this one myself. I'm capable, but I'm afraid the darn thing would be torn apart in my garage for weeks before I figured it out and found the parts needed to repair it. So I'm taking it to a mechanic next week - an old time Mercedes guy who is familiar with this system and has the knowledge and tools to get the job done. Not sure what all is wrong in there - the car is 22 years old and there have been problems with the ventilation for a while now. Could be more than just the center vent vacuum actuator. I may also have a problem with the fresh air / recirculate door. That door has a return spring that is prone to fatigue failure - it breaks, resulting in the door not closing, and apparently this can cause excessive moisture build-up in the cabin, which I have experienced lately. Replacement of this spring appears to be a difficult task. We'll see. Anyway - thanks, and I will post the results of my visit to the mechanic in a couple of weeks.

fatherfixit
 

·
Registered
1995 mercedes C220 base model
Joined
·
16 Posts
great

please do post the results, a happy conclusion to problems is the most important thing!!
 

·
Registered
1996 C220 2007 ML320 CDI
Joined
·
1,830 Posts
I've replaced all the vacuum actuators myself and it's not a complicated job. You don't need any special tools, just some sockets / screwdrivers. It's just a long job, it takes a full day.
 

·
Registered
1998 C280 - 400,000 miles
Joined
·
32 Posts
Discussion Starter #6
Good to know. I go by "fatherfixit" for good reason, but unfortunately I am recovering from rotator cuff surgery on my right shoulder and will need to have someone do it for me this time (it gets hot here in the summer and I'll need the ventilation working). Did you test the actuators before replacing them or just do them all as a matter of course? Where did you get the parts? Also what about that fresh air/recirculate door - were there any issues with the return spring on yours?
 

·
Registered
1995 mercedes C220 base model
Joined
·
16 Posts
you can remove them and test them to see if they hold vacuum if you got a mighty vac.... but i basically isolated my problem to either the change over block/vacuum element that controlled the center vents because that was the only one i had problems with, all other vents/climate control features worked fine



I took a stab in the dark hoping it was the change over block and changed that out first because it didnt require removal of the dashboard but it did not correct the problem. After this i knew it was time I had to pull the entire dash so I pulled it apart and I replaced the bellow circled in red in the photo i uploaded

after mulling over it I left the dash apart for a while and ordered the rest of the bellows before putting it all back together so I knew everything in there was new, did NOT want to do this twice.
there was no issue with my fresh air/recirculate door or return spring from what i could see

I sourced all my parts from ebay there are plently of BEHR/HELLA brand parts that are quality, not sure if they are the original parts used in the car though. Just check the original part #/manufacturer part #s between listings carefully if you are going to buy on ebay to make sure you dont end up buying the same part twice

I had noticed on removing my dash some in the car were BEHR and others were unlabelled so im not sure what is used for an OEM part
 

·
Registered
1996 C220 2007 ML320 CDI
Joined
·
1,830 Posts
Good to know. I go by "fatherfixit" for good reason, but unfortunately I am recovering from rotator cuff surgery on my right shoulder and will need to have someone do it for me this time (it gets hot here in the summer and I'll need the ventilation working). Did you test the actuators before replacing them or just do them all as a matter of course? Where did you get the parts? Also what about that fresh air/recirculate door - were there any issues with the return spring on yours?
I did not have any issues with the springs, they were all solid. I got the parts from a few different places online, make sure you get the Behr parts when you can, it's the OEM and much cheaper than the exact same Genuine MB branded part. I've had to go Genuine for a few of the actuators, it depends on what you can find. I got mine from FCPEuro. For anyone wondering, I paid somewhere between 300-350 for all the parts + shipping, and it's 100% worth doing all of them, you don't want to have to pull the dashboard off a second time. To be fair though, now that I've done it once, it would take me much less time to do it a second time.

I did test them, but honestly, the internals are made from rubber, so even if a few of them didn't leak... they aren't too far behind from those that are. And it's best to snatch up new parts before they're gone altogether, I can't imagine anyone is making these anymore ;) At least now my HVAC is good for another 20 years :D
 
1 - 8 of 8 Posts
Top