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1989 190e 2.6 1993 500sel (sold) 1995 S500 coupe (sold) 1994 S500 blk/blk
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Discussion Starter #1 (Edited)
This commentary applies to a 1994 S500 and may apply to other earlier W140's.

The vehicle has 194k on the odometer. At any rate when I purchased the car, everything worked except there was a lack if air flow in the side vents and foot wells. Worked fine in the recirculation mode, but when I switched that off it seemed like the air flow was going nowhere even though the blower motor was working. The motor was starving for air.

Problem it is and a familiar problem on this forum, and after a lot research I read of posters' problems with this phenomenon but there never was a solution given. And I read many, many of them.

Some solutions (thanks Brett) given are to remove the glove box lining and to check the switchover valve unit (behind the lining) which is activated by the push button control on the dash. I did this and found no problems but the unit was not firmly attached. Reattached it and replaced the liner, a simple procedure.

I then removed the front passenger foot well to look for problems with the vacuum distributor block. None were found. Looked clean and new in there.
Reattached the cover. Another simple procedure.

Then I raised the hood and removed the cowling (actually the plenum) exposing the cabin air filter.
Upon examination I found the source of the problem. I removed the filter, checking the blower motor. I started the car with the filter removed and wow! Air pored out of all inside vents. I shut off the engine knowing that all the air distribution vents were working.

Then I examined the plenum and found that the fresh air vent was closed!
The cause was that the arms of the two vacuum motors were disconnected from the vent so the vent remained closed at all times only allowing a a seepage of air to the blower motor but allowing the recirculation mode.

I had to haywire the connections until I can find the correct ones. Put the plenum back on. Started the car, drove it, tested all of the push buttons and it all worked, had plenty of air flow. Problem solved.

However as a further commentary, I noted that there are two rain drain hoses on the plenum. One is next to the PCV valve and the other is close to the cabin filter. The one next to the PCV valve was missing.
The one next to the cabin filter was deteriorated. Both are proprietary hoses, very soft and pliable. I was able to get the MB part number for the deteriorated hose.

One more problem remains: the temperature adjustment wheel on the passenger side when set to HIGH cools, When set to LOW heats--just the opposite of the driver's side. I can live with this by making adjustments, but I would like to know the cause.

Finally, I discovered in all of this the user friendly DTC code reader next to the
exterior filter area. Will now teach myself how to use it. I understand that this feature was discontinued in 1995 models.

Sorry if this is long and perhaps boring, but others who are having a similar problem may find this commentary useful.
 

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Thank you! I've had this same issue and thanks to you went right to the actuator flap today and sure enough - the arm from the actuator and the arm connected to the flap weren't connected. Two small plastic bushing things were lying on top of the cabin filter so I imagine they were pressed into the holes of the arms. I used a small zip tie to connect them with enough slack to allow free movement. It is now working perfectly!

Thanks again!
Brian
 

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1989 190e 2.6 1993 500sel (sold) 1995 S500 coupe (sold) 1994 S500 blk/blk
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1,007 Posts
Discussion Starter #3
Thank you! I've had this same issue and thanks to you went right to the actuator flap today and sure enough - the arm from the actuator and the arm connected to the flap weren't connected. Two small plastic bushing things were lying on top of the cabin filter so I imagine they were pressed into the holes of the arms. I used a small zip tie to connect them with enough slack to allow free movement. It is now working perfectly!

Thanks again!
Brian
Brian, I am happy that this worked out for you!
 

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1997 CL500
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How do you remove the lining from the glove compartment, and how do you remove the lining of the front passenger side floor ?
Thank You
 

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1989 190e 2.6 1993 500sel (sold) 1995 S500 coupe (sold) 1994 S500 blk/blk
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1,007 Posts
Discussion Starter #5 (Edited)
How do you remove the lining from the glove compartment, and how do you remove the lining of the front passenger side floor ?
Thank You
Open the glove box. Pry off the light fixture. Look closely and you will see two plastic fasteners at the bottom of the glove box. Pry them off. Then feel around the top and edges of the lining for two or three other fasteners.(the tops of these fasteners may be camouflaged with the same stuff of the liner) Pry them off with either a knife blade or small flat end screwdriver. All of these fasteners come off easily. Check to see if the lining is loose, then using a flat screwdriver pry up on the front tabs right and left and pull out the lining.
Reinstall.

The passenger side foot well? Pull back the carpet from the top. You will see a large metal shield. Remove the two bottom nut fasteners and slide the shield slightly downward after you have lifted the bottom of the shield from the protruding nut holders and then pull it forward carefully. You will then see the guts of wiring and plastic vacuum lines. No need to pull the shield completely out. Depends though on what you want to do in there.

Nothing complicated about either of these procedures, but it is necessary to have a good light when working especially on the glove box.

Please remember that this is for a 1994 S500. Maybe slightly different for your 600.
 

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1997 CL500
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1,210 Posts
Open the glove box. Pry off the light fixture. Look closely and you will see two plastic fasteners at the bottom of the glove box. Pry them off. Then feel around the top and edges of the lining for two or three other fasteners.(the tops of these fasteners may be camouflaged with the same stuff of the liner) Pry them off with either a knife blade or small flat end screwdriver. All of these fasteners come off easily. Check to see if the lining is loose, then using a flat screwdriver pry up on the front tabs right and left and pull out the lining.
Reinstall.

The passenger side foot well? Pull back the carpet from the top. You will see a large metal shield. Remove the two bottom nut fasteners and slide the shield slightly downward after you have lifted the bottom of the shield from the protruding nut holders and then pull it forward carefully. You will then see the guts of wiring and plastic vacuum lines. No need to pull the shield completely out. Depends though on what you want to do in there.

Nothing complicated about either of these procedures, but it is necessary to have a good light when working especially on the glove box.

Please remember that this is for a 1994 S500. Maybe slightly different for your 600.
Thank you very much for the information.
 
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