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  #1  
Old 11-10-2002, 06:23 PM
RON FINLAY
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Little electric motor/fan behind the dash

There is an electric motor with some sort of fan (cannot see unit, only feel) located behind the dash under the ac/heater vent outlet on the passsenger side. It appears to have some type of hose mounted to the rear of the unit. It is probably failing as it makes an annoying noise while running, which is all the time.

Can anyone tell what this device is? Will the car "self destruct" if it disconnected? It is hard to get to and I cannot locat any bolts that attach it to the rear of the dash.

Any thoughts appreciated - Ron
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  #2  
Old 11-10-2002, 06:47 PM
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The fan...

...sucks in cabin air for the climate control sensor to adjust the automatic air cotrol (A/C or heater) foor your car. If you disconnect it, the car won't self-destruct, but your A/C or heater won't work right. I think there is a post, in the DIY section on how to test it to see if it is working properly. but if yours is making noise, then it is time to change it.

The whining noise is really annoying. I replaced the fan in both my daughter's 300TE and in my 420SEL.

Do a search and you will find plenty of info on this issue.

Good luck.
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  #3  
Old 11-10-2002, 06:57 PM
DHA DHA is offline
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ditto to previous reply. Take a glance at this site:

ACC Sampler blower motor not samplin'!

The key phrase is: "sampler blower motor." Fast lane sells replacements. I'd try cleaning it out first.

Don't disconnect the unit; you'll have all sorts of grief trying to to regulate the Climate Control System.
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  #4  
Old 11-10-2002, 08:01 PM
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That little fan motor behind the passenger side air vent is called the aspirator motor.

It sucks in air and blows it up the A pillar, through the headliner, and out through the vent that is right next to your dome light / sunroof control button.

The temp sensor for your a/c is up there, which registers the temp for your wheel, and also blower speed.

My mechanic replaced mine two weeks ago. It looks like he inserted some thin plastic stick into the air vent and inside tab in the air vent on each side, pulled the tabs toward the middle, and the plastic vent pulled right out.

He could pull the aspirator motor right out so that we could see it and hear it run. Mine was noisy.

He simply unplugged it and installed a new one. Took all of 20 minutes.

He explained they go out all the time. He replaces them a lot on C classes, too. He had one from a C class on his desk, and it was tiny. They are just able to make parts smaller and smaller to save money, and weight.
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  #5  
Old 11-10-2002, 09:26 PM
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I just joined the Mercedes Benz Club of America, and found this nice article on how to remove those side vents:

http://www.mbca.org/pages/tech/MBCA_Remove_dash_vents.htm
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  #6  
Old 11-10-2002, 09:40 PM
RON FINLAY
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Thank you all for your input. After posting, I went to a Performance Catalog and found the little sucker. I do not buy from Performance, but their catalogs are great for helping identify and locate parts.

Ron
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  #7  
Old 11-11-2002, 02:00 AM
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Not sure which car you're talking about here, but if it's a 126 replacement is a snap.

Open and empty glove box. Remove the centers from the seven "plugs", then pull the plugs. Disconnect the glove box light and remove the glove box liner (it will take a bit of tugging - tight fit). Once the liner is out, you'll see the sampler blower just behind the vent. One hose and one two pin connector. The blower just snaps into a mount.

Word of caution, it is easy access but a tight fit depending on hand size. I had to use two hands to reconnect the hose and found I drew a little blood on the back of my hand, where it rubbed against the sharp edge of the glove box opening.
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  #8  
Old 11-12-2002, 08:44 PM
RON FINLAY
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Mike - thanks for the info. I already had the glove box out and was finally able to figure out how to pull the fan. It is a tight fit!

Ron
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  #9  
Old 11-13-2002, 02:50 AM
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Paul,
I thought that if your car had an airbag, you had to remove it in order to get to the fan. Does it simply just require you to remove the passenger side vent?? I think I need a new fan and am very hesitant to mess with airbags, so this may be good news for me.

THanks,
Matt
'94 E320
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  #10  
Old 11-13-2002, 02:55 AM
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Also, does the vent next to the sunroof controls actually suck air into it, or blow air out of it??

Thanks,
Matt
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  #11  
Old 11-13-2002, 06:59 AM
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Matt, it sucks air into the vent. The in car temp sensor is located inside the vent.
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  #12  
Old 11-13-2002, 10:23 AM
Bud
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Please bear with me because I want to understand how this works. The HVAC sensor is inside the small vent near the sun roof controls. Air is drawn past it and flows down the curbside A-piller. The small motor drawing the air is located adjacent to the glove box.

Where does the air exit? Does it make any differerence if the passenger side air vent is closed? How much air flow should be expected, i.e. using the kleenex test?

TIA, Bud
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  #13  
Old 11-13-2002, 12:35 PM
DHA DHA is offline
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Little Electric Motor/Fan Behind Dash

The volume of air being moved by the little motor-fan assembly is very small. As I recall, that unit is 2 - 3 inches in size. The small amount of air is expelled into the area above the passenger's feet. Mine runs all the time, ACC or no ACC.

I too had concerns that this little motor had quit. My 126 has air bags, so I was reluctant to probe around the area of the passenger's air bag to find this motor/fan. Curiosity got the better of me for a collection of reasons.

From memory, working from the passenger's footwell, to access the little fan (which is located next to the main ACC blower plenum) remove the 3 ? vertical screws that hold the knee bolster/change tray in place. Then pop out the plastic face plate/escutcheon in the passenger's change tray to remove some remaining screws (in this 126 I have learned that escutcheons should generally be lifted out from their right side, pivoting at their left side). The air bag wasn't an issue since it is mounted well above this area.

It's been awhile, but I believe the visible little motor is then accessible. If not, there are 3 bolts that hold the passenger side metal ACC plenum in place. ( The 3rd bolt is cleverly accessed with an extension on a socket wrench) Removing that plenum exposes the little motor in question.

In retrospect, to check the viability of that little motor is easier done by using the often mentioned tissue paper test. Since the suction is so weak, I found that it was a more certain test if the overhead grill and light assembly were lifted out, the plastic tubing to the temperature probe removed, and the tissue paper placed over the open plastic tube. If the paper sticks, the motor and fan are functioning. I am guessing, but I don't think that its necessary for this whole assembly to be so powerful that it will draw inches of vacuum.
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  #14  
Old 11-13-2002, 01:09 PM
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Quote:
Originally posted by mcdill
Paul,
I thought that if your car had an airbag, you had to remove it in order to get to the fan. Does it simply just require you to remove the passenger side vent?? I think I need a new fan and am very hesitant to mess with airbags, so this may be good news for me.

THanks,
Matt
'94 E320
I watched my mechanic remove my aspirator motor on two separate occasions. Once to pull it out to diagnose the problem, and then the following weekend to install the new one. The passenger side airbag is not removed. With the help of a flashlight and plastic sticks, he pulled on the tabs inside the vent, and pulled the vent out. He reached in with his hand and pulled out the aspirator motor. He disconnected the cord, installed the new one, pushed the motor back into place, and snapped back on the vent. It took maybe 20 minutes.

It seems obvious from Mike and DHA's posts that doing this on a W126 might be different, but the way it is removed on a W124 is exactly as I have described. The link I posted on the mbca.org website describes this in the same way that my mechanic did it.

From what my mechanic said, I walked away with the understanding that the temp sensor is up in the headliner near the vent opening, and that air is sucked up through the side air vent, not the other way around.
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2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".
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  #15  
Old 11-14-2002, 08:43 PM
RON FINLAY
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It is amazing how one little question can get so many inquiries. Since I am dealing with an older 124, I do not have an air bag on the passenger. I could see where that might pose a problem. Getting to the motor/fan is easy if the glove box is removed.

At any rate, I have stopped, probably just temporarily, the noise the motor makes by applying some synthetic oil at the point where the shaft enters the bearings at each end. I removed the motor from the housing to do this. The bearings appear to be the oil impregnated type. It has made it run smoother and does not make the noise anymore.

Ron
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