The center vents should blow equally as forcefully as the side vents.

__________________
1983 300D Midnight Blue
4 speed, W115 intake mani, non-EGR exhaust mani, KKK K26, 3 pc Euro bumpers, Lo-spec Euro headlights, AL129X, hubcaps, custom A/C

1987 300TD Smoke Silver
Euro headlights, thermostat relocation, coolant bypass mod, rebuilt Becker + Jehnert + Helix audio, OEM Oris roof boxes and surfboard racks, Euro towbar

1983 300TD Reed (Moss) Green / Dark Olive MB Tex Euro spec

1983 300TD Silver Blue / Blue cloth Euro spec, OM648 and 722.6, 15" hubcaps, W126 S2 brakes

It is pink and buried in the dash.
You can't get to it easily unless you remove the whole dashboard.


Some reading:

PeachPartsWiki: Replacing the A/C Evaporator

W123. My experience with replacing all AC vacuum elements without removing the dash.

__________________
1983 300D Midnight Blue
4 speed, W115 intake mani, non-EGR exhaust mani, KKK K26, 3 pc Euro bumpers, Lo-spec Euro headlights, AL129X, hubcaps, custom A/C

1987 300TD Smoke Silver
Euro headlights, thermostat relocation, coolant bypass mod, rebuilt Becker + Jehnert + Helix audio, OEM Oris roof boxes and surfboard racks, Euro towbar

1983 300TD Reed (Moss) Green / Dark Olive MB Tex Euro spec

1983 300TD Silver Blue / Blue cloth Euro spec, OM648 and 722.6, 15" hubcaps, W126 S2 brakes

That is it.

__________________
1983 300D Midnight Blue
4 speed, W115 intake mani, non-EGR exhaust mani, KKK K26, 3 pc Euro bumpers, Lo-spec Euro headlights, AL129X, hubcaps, custom A/C

1987 300TD Smoke Silver
Euro headlights, thermostat relocation, coolant bypass mod, rebuilt Becker + Jehnert + Helix audio, OEM Oris roof boxes and surfboard racks, Euro towbar

1983 300TD Reed (Moss) Green / Dark Olive MB Tex Euro spec

1983 300TD Silver Blue / Blue cloth Euro spec, OM648 and 722.6, 15" hubcaps, W126 S2 brakes

If you do this, then make sure you cap off the vacuum line that goes to that pod, so you don't have a vacuum leak.

__________________
1983 300D Midnight Blue
4 speed, W115 intake mani, non-EGR exhaust mani, KKK K26, 3 pc Euro bumpers, Lo-spec Euro headlights, AL129X, hubcaps, custom A/C

1987 300TD Smoke Silver
Euro headlights, thermostat relocation, coolant bypass mod, rebuilt Becker + Jehnert + Helix audio, OEM Oris roof boxes and surfboard racks, Euro towbar

1983 300TD Reed (Moss) Green / Dark Olive MB Tex Euro spec

1983 300TD Silver Blue / Blue cloth Euro spec, OM648 and 722.6, 15" hubcaps, W126 S2 brakes

Funola,

Before you go and start disassembling your dash, try this instead.

Pull out the glove box and the passenger foot panel. Look inside at the various switch over valves that live towards the rear. Using the FSM, find the line that feeds to that impossible to reach vacuum pod for the center vents.

Take a look at the rubber connectors. Do you see what look like red "rings" over top of the rubber arms?

If so, yank off the rubber connector arms and apply vacuum to the pod. With a flash light, see if you can get the pod to actuate by applying vacuum.

On my 380sl, I discovered that there were these red rings that were placed over top of the rubber connectors. They were put there to restrict vacuum so the pods wouldn't slam as hard when called to action.

The red rings ended up collapsing the rubber to the point where the pods wouldn't work anymore.

Ironically, there is an updated version where they use an "orifice" and the blue/black one way valves in order to achieve the same effect.

I replaced all of the rubber connectors, put in the updated orifices, and blue/black one way valves, and was surprised to see that all of my vacuum pods were working correctly! Thank goodness because I was not looking forward to yanking the dash out.

Also, you could have a bad switch over valve. Another potential fault worth investigating.

Do this first before committing to the dashectomy. .

__________________
-Typos courtesy of my mobile phone.

Thanks for the links. I've seen these two Morrison epic threads before but never looked at them in detail because I never had the need to till now. They are coming in handy.

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Thanks! I never pull stuff apart unless I have gone through the diagnosis first.

I pulled the glove box liner and the under panels. The center vent vac element is really buried in there!

I started the engine to charge up the vacuum and operated the AC panel switches. I can see the main air flap vac element (the one right below the glove
box) open and close no problem. The center vent element is not moving at all when I work the switches.

My next step is to get access to the vac solenoid for the center vent element where I can check the solenoid and where I can access the vac line that connects to the center vent element in order to check it with a MityVac.

Is removing the antenna switch panel enough to access the solenoids or do I need to remove the console?

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Assuming you can trouble shoot and it is indeed that center pod, this is the one scenario where I think a “hack” repair is actually an upgrade. I’d just cap the vacuum to that pod and prop it open. Super soft plastic that’s easy to put a screw into, to hold the flap open. I have pics elsewhere.

It’s a personal thing I guess, but I always like air by my face and coming out of the dash vents. Bi level is rare and feet only is even more rare. Defrost is only occasionally useful in any of my cars.

For me, the center vent just stopped working due to sitting in a garage for six years. But in looking at my options, it seemed ideal. And IMO it is.

But if you have a vac leak, be sure to fix that or cap it.

I’d go in to fix any other dash vac pods. It’s just this center one that I can easily manually close, and generally like open.

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Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1985 190D (169k)
1991 350SD (113k)
1991 350SD (206k)
1991 300D (228k)
1993 300SD (291k)
1993 300D 2.5T (338k)
1996 Dodge Ram CTD (442k)
1996 Dodge Ram CTD (265k)

Past Diesels:
1983 300D (228K)
1985 300D (233K)

I disconnected the vac Tee with 2 vac lines on it (Red/black and Red/blue) on the center vent element and hooked my MityVac directly to the element. When I pumped the MityVac, the rod did not move nor did it hold vacuum. To be sure I interpreted the results correctly, I tested a good element the same way and saw its rod move and it holds vacuum. So I have a confirmed leaky center vent element.

JHZR2, did you jury rig the center flap open w/o removing the dash?

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

I unfolded the center vent rubber boot and was able to reach in with my fingers, and with some difficulty fighting spring tension, open the flap. Is the spring tension exerted by the element? Or is there a spring on the flap to keep it normally closed?

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

The tension on the center flap is created by the vacuum pod.

Thanks! There's not much room to work in there. What's the easiest way to prop the flap open? I'm not sure how easy it is to pop that plastic pin off the rod. Once the pin is out, isn't the rod still in the way for the flap to be propped open?

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

What do you think of drilling two 1/8" holes in the rod with a long drill bit. One hole is used to pry the flap to the open postion. Insert a coat hanger through the other hole on the outside on the box to keep the flap open.

Attached Thumbnails

 

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Another idea (no hole drilling) is to use a long nose vise grip on the rod to keep it open.

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

I am really not one for jury rigging a function, however you might try opening the flap all the way and then using a small diameter wooden dowel to hold the flap open from the front of the vent.