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  #1  
Old 11-17-2012, 05:32 PM
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New (to me) '84 300D - no air flow thru vents

I 'inherited' this car - pretty nice shape. Just got some stuff back together and I've got some issues. The blower motor runs - both hi and lo speeds but I'm just not getting any air flow anywhere. The center vents won't open, although I can hear them "clicking" - like they're trying to open...

But, I don't have much air air flow at all from the defrost or side vents either. I just tested all the pods and didn't find any leaks. Really confused - any ideas?

ryan

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1991 300CE
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  #2  
Old 11-17-2012, 09:50 PM
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Debris-filled cowl intake ducts?

Vacuum failure elsewhere, like in the central locks?

Divide and conquer and isolate any vacuum leaks. I'd try to route all vacuum to the green line and see if you get control of the pods.
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  #3  
Old 11-17-2012, 09:58 PM
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Just got done troubleshooting locks - they seem to be working ok now. Hadn't thought about checking the cowls - will do so in the morning... I am also having a hard, delayed shift problem...

One observation - I had the vacuum pod that controls the recirculation door (far right under the glove box) out of the car. It was not leaking and rubber diaphragm was in good shape. But, I noticed that I couldn't pull a vacuum on it unless I slightly depressed the rod first - then applying vacuum pulled the rod all the way in and it held fine.

Drove it some tonight and I keep hearing a clicking noise right behind the center vents - sounds like the door is trying to open...? Or maybe a switchover valve??

I will try and route vacuum to the climate control line and see what happens...
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1984 300D
1972 250
1986 560SL
1991 300CE
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  #4  
Old 11-17-2012, 10:02 PM
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Quote:
Originally Posted by rgnprof View Post
I am also having a hard, delayed shift problem...
Vacuum leak....

Quote:
Originally Posted by rgnprof View Post
One observation - I had the vacuum pod that controls the recirculation door (far right under the glove box) out of the car. It was not leaking and rubber diaphragm was in good shape. But, I noticed that I couldn't pull a vacuum on it unless I slightly depressed the rod first - then applying vacuum pulled the rod all the way in and it held fine....
I have seen this MANY times. It stems from a vacuum leak between the PLASTIC piston and the RUBBER bellows. I got in the habit of cementing the rubber to the plastic with 3M trim adhesive or Gaskacinch during service and that eliminates the issue....
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  #5  
Old 11-17-2012, 10:13 PM
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What do you mean "plastic piston"?

ryan
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  #6  
Old 11-18-2012, 07:05 AM
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New(to me) '84 300D-no air flow thru vents

The center vent pod is most likely evacuated through a restrictor in the Y connector(look for a red dot or band on it) which I think was used by MB to prevent noise from the vent door rapidly opening and closing, annoying the well heeled owner. With the restrictor in place, a very small leak in the diaphragm or pod will prevent it from opening as the restricted vacuum supply cannot overcome it. Sometimes it may open part way but not fully. Movement of the piston/diaphragm might also open up the leak, explaining the clicking that you are hearing.
Peter
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  #7  
Old 11-18-2012, 01:39 PM
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Another center vent, clicking observation...The clicking is pretty constant at speed - NOT when idling. Also, it clicks regardless of whether or not the climate control is even turned on...

ryan
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Old 11-19-2012, 12:48 AM
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Quote:
I got in the habit of cementing the rubber to the plastic with 3M trim adhesive or Gaskacinch during service and that eliminates the issue....
Can you elaborate on where to glue?

Ryan
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1984 300D
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  #9  
Old 11-21-2012, 12:55 AM
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I think I figured out the glue issue, but in re-examining the rubber diaphragm in the fresh air/recirculating pod, I noticed a tear. I have ordered replacements from George Murphy.

I talked with the PO and this was his email response to my question about the air flow and vents issue:

"The vent problems all started when I put the blower motor back in after I replaced the brushes. I followed the directions in the Mercedesource.com repair manual to replace those brushes. It's always possible that I reinstalled the motor backwards and the air is blowing against the housing instead of out of the vents. That's the first thing I considered, but I thought the housing would only go in one way because of the way the bolts were placed. It's not too much trouble to drop it out and that might be a simple explanation for why no air is circulating."

Anyone help here? I'm still at a lost...the clicking noise in the center vents is constant - except when idling and tonight, I noticed that it stops when in EC AND heat. Turn the temp dial cooler and the clicking starts up again - driving me nuts!

I just have no significant air flow from anywhere...

ryan
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1984 300D
1972 250
1986 560SL
1991 300CE
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  #10  
Old 11-24-2012, 11:25 AM
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Bump!

Anyone got any ideas here - I have attached a pic of the blower - what direction is this fan supposed to spin - CW or CCW?

I have no air flowing - in any volume - thru any of the vents, although the blower motor runs great. The clicking noise that I have referenced earlier in this thread, I have noticed, goes away when i adjust the temp valve to heat (usually greater than the 22C setting...

Any help would be appreciated.
Thanks.
Ryan
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New (to me) '84 300D - no air flow thru vents-blower.jpg  
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RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE
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  #11  
Old 12-04-2012, 06:47 PM
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No one can help here?

I am still confused...I draw a vacuum on the green/yellow line that goes into the cab through the firewall and it holds indefinitely - no leaks. Got the recirc pod fixed with some diaphragms from George Murphy, but I still have no air flow...and I still have this clicking behind the center vents.

If you read through this thread, is it possible that the blower motor is spinning the wrong way? I have no appreciable air flow anywhere - even in full defrost.

Ryan
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RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE

Last edited by rgnprof; 12-04-2012 at 11:11 PM.
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  #12  
Old 12-04-2012, 09:32 PM
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Its apparently not an area many of us have had problems with.
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  #13  
Old 12-05-2012, 10:20 PM
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Well, I finally figured it out. When the PO put new brushes on the motor, somehow the wiring got crossed in the re-installation. The fan was running clockwise, which as it turns out is WRONG. I plugged the fan in to the connector the opposite way and the fan started running counterclockwise - which is right! Made all the difference in the world!

I also discovered that the center vent pod rubber diaphragm was leaking - I got the pod out w/o too much trouble, but I lost all of the rubber washers and press washers in the process - and I lost whatever connects the pod to the flap in the center vents (a rivet, I guess...). The rubber washers shouldn't be too much trouble to find, but I couldn't find the right size press washers. I did find some E clips that might work. Any idea where I can get the washers? Or any suggestions on how to reconnect the pod rod to the center vent flap?

Ryan

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1991 300CE
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