PeachParts Mercedes-Benz Forum

PeachParts Mercedes-Benz Forum (
-   Tech Help (
-   -   1996 E320 AC Vents dont seem to respond well, airflow weak despite change in fan spd (

Machnumber2 01-17-2010 03:37 AM

1996 E320 AC Vents dont seem to respond well, airflow weak despite change in fan spd
I am kind of stuck on trying to figure out this problem and welcome any ideas.
I have a 1996 E320 Mercedes. On the ac control panel, when I adjust the fan speed to blow more air, the airflow doesnt seem to change very much even though you can hear the fan going faster. Also there is a button with 3 arrows I think, the up arrow I think means for air to blow up, the side arrow is for air to blow in the car and the bottom arrow for the airflow to be directed downwards. Changing the settings on this button seems to have little to no effect on the air coming into the car, especially with the vents that blow horizontally into the cab. I was wondering, what coud be causing this? Are there damplers controlled by acutators that control the airflow? Are they powered by vacuum and could there be a vacuum leak that is causing this problem? I do not notice any hissing sound when it runs.
Thanks in advance, I look forward to hearing any thoughts about his.

Cal Learner 01-17-2010 12:08 PM

If the fans in the "squirrel cage" are installed backwards, it'll do what you're describing: lots of fan noise but very little airflow. Has the blower fan been worked on or replaced recently? If so, it's worth a shot to find out if the cages were reinstalled correctly.

Machnumber2 01-17-2010 01:48 PM

I had never thought of that, I agree that is what would happen. Is that possible though, given the shape of the fan to put it on backwards?

mpolli 01-17-2010 02:17 PM

Have you checked the cabin filter? I am very skeptical about the backwards fan theory...

Machnumber2 01-17-2010 02:34 PM

I got a PM indicating the filters as well, and found some excellent information here:

Matt L 01-17-2010 04:25 PM

There is a vacuum diverter valve buried in the dash which controls the flaps. That may be bad. But it's expensive enough that you don't want to swap it out to test. If it's good, your climate-control pushbutton unit may be at fault.

Are you sure that your fan is blowing faster when you increase the control past half-way? If not, you could have a bad blower regulator, which is a very common problem on your car.

Machnumber2 01-17-2010 05:10 PM

So far I have ordered the filters here and hope that fixes the problem. The fan speed does seem to change when I adjust the fan speed settings.

I tried to find the part here for a vacuum diverter valve, I hope that is not the problem but it might be. Is this pretty difficult and expensive to replace? Do you know what the part # is so I can price it?

Machnumber2 01-21-2010 11:11 PM

19 Attachment(s)
I thought I would post the photos of changing the filters, it was not so bad. I did not have to pull very hard, it kind of clicked out and then clicked back in when I was done. The filters were very dirty. However the problem has not been solved, the airflow is the same. I am going to do another post down further listing some other symptoms the car is having that might be related to the low airflow. Here are the photos of replacing the filters...

Machnumber2 01-21-2010 11:20 PM

The car also experiences these symptoms...
The windows roll up very slowly, especially the front passenger window. Occasionally in the morning when the car is first started, the engine will turn over very slowly and sometimes start barely or die. If you turn the key on and off it usually then starts normally. The power antenna does not work. The radio comes on even if the key is off and out but I think that might be normal.

The car runs great overall. I am not even sure if there is even a problem, but the windows going up that slow and the fan being that slow seem odd, like its a low voltage condition, but the car starts ok.

Any ideas that it could be low voltage? The battery is relatively new, but had to be replaced a couple of years ago I think because of that starting thing I mentioned above.

I also plan to look into the vacuum diverter valve someone mentioned above. Any ideas appreciated, thx.

gmercoleza 01-22-2010 09:08 AM

Maybe I'm stating the obvious. Are you certain the vents are set to "on" on the slide rollers?

gmercoleza 01-22-2010 09:09 AM

As for the filters, I would have just removed them to rule them out. Cheaper and faster than buying new ones (unless of course you need new ones anyway, which it appears you did).

Machnumber2 01-22-2010 10:54 AM

Well I figured the filters were likely to be pretty dirty anyway since they have not been replaced since we have owned the car.

We did try all the sliders, I even shined a flashlight in there to be sure I could see how the dampers were moving as I moved them. Like someone else here said, there are 3 positions, full open, almost closed and fully closed. No luck there.

I was checking out last night but the site may have been having a problem because all the fields were blank no matter what type of car I typed in. I would like to find out how much work its going to be to replace some vacuum elements. Maybe get a vacuum tester but I have never used one and at the moment dont see how they are used to actually locate a vacuum leak. Please keep the ideas coming.

jcyuhn 01-22-2010 11:03 AM

Slow cranking sounds like a classic battery on the way out symptom. Many auto stores will test the battery and charging system for free. They roll a cart with a load tester out to the car. Note that a battery can have good voltage, ie lights are bright and such, but still be failing. The load tester checks the voltage drop while delivering several hunderd amps of current, simulating what occurs when cranking the engine. That will call out a failing battery.

It's normal to be able to turn on the radio without the key - just push on on/off/volume knob. It's a feature, not a bug. :)

I have no clue on the low airflow issue...

Machnumber2 01-22-2010 11:28 AM

I hope its not the battery, its around 2 years old, maybe 2 1/2 it should have plenty of life left or there is an electrical problem somewhere although the car seems fine otherwise.
On another note I got to work. However so far I cannot find the diagrams that show how to get to and replace the vacuum elements.

gmercoleza 01-23-2010 08:52 AM

Where are you located? 2.5 to 3 years may be all you get in a warmer climate.

All times are GMT -4. The time now is 04:07 PM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2022, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website