On my 85SD, the switchover valves are numbered top to bottom 15,14,13, 18,17,16. I may have the order reversed as I'm looking at the attached diagram. Anyhow, the 2nd valve either controls pod for the legroom flaps OR pods for fresh air recirculation from the center flaps.

Attached Files

Pages from 83-604.pdf (75.8 KB, 274 views)

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

Keep in mind that there are 3 positions of the fresh air/recirculation flaps: 100% fresh air, 80% recirc/20% fresh, and 100% recirc. This is accomplished with the large-lift and small-lift vacuum elements.

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2002 E320 T-sedan (210.282) 219K
1994 E320 (124.032) 252K (dearly departed in hit & run)
1988 260E (124.026) 301K (sold)

Just disconnect the defrost flap arm from the vacuum element. It is to the left in the glovebox. you can then either open it or shut it all the way. I left my glovebox liner out until I replace that element.

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77' 300D, "Cartman" SOLD @ 150K (didn't know what I had)
83' 300SD, "The Superdon" 325k+ @ 28mpg
95 E320 wagon, "Millennium Falcon" 231k+ @ 24 Mpg
95 E300D, "Sherley" 308k @ 33.69 Mpg, currently anticipating a head
99 Suzuki Intruder "Trudy" @ 45 mpg

I have now tested my CC iaw the FSM and everything tested good. I was stumped till I went back to the first test it calls for. The test the check valve in the engine compartment.



I found these vacuum hoses hard and brittle and the one on the right was disconnected (shaken loose, probably) After i connected it again everything works as it should!

I am off to find some vacuum line now.

On a side note, there should be a check valve here, but all I see is a filter of some sort. To the right of it the hose routes up to the firewall and to the left it splits and goes in front of the engine and around to these, right behind the passenger headlight where I found some more cracked hoses to be replaced. Anyone know what these are? I will try to dig around in the FSM, but it seems my car is slightly different then the pics in there (maybe because it is an 85?)

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----Adam

1985 300SD 322,000

4:
As I recall the No. 2 nipple on the "shuttle valve" (which is what it really is) went to Pod #39, which on mine is leg room flaps. Pod #38 goes to the #1 nipple. Pod #38 is defrost flap. I disconnected the Pod actuator rod to the lever arm on defrost flap. Closed the flap and hot melt glued it to the plastic housing. See first photo in this thread that shows pod.
Also on mine, Pod #38 has two vac. lines. End and side. The end line is color coded Red/White stripe. The side one is Red/Light Blue stripe. Capped the shuttle valve nipple and pod side hose with standard vac. line cap and plug. From Autozone I think. Old school option is short piece of rubber vac. line and sheet metal screw for cap, and golf tee for plug.

Dave

Hot melt glue. And, its always removable without too much effort.

The problem you might be seeing is the Defrost, along with the Fresh/Recirc pods, is a "long throw" pod that has two sections. One section may hold the vacuum just fine but the second may leak causing the flap to not close fully. Many have tried to rebuild the long throw pods, including myself, but it doesn't seem to last. It's easier, and less frustrating to replace the pod....available here at Fastlane.

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Sam

84 300SD 350K+ miles ( Blue Belle )

One very key question : What is the vacuum supposed to be there ?

15" sounds pretty low. You should have ~29" right at the brake booster under the hood.

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1985 300D 198K sold
1982 300D 202K
1989 300E 125K
1992 940T

"If you dont have time to do it safely, you dont have time to do it"

"The democracy will cease to exist when you take away from those who are willing to work and give to those who would not."

That's a good question. On my initial investigation I found ~18" from the hoses with the car running with A/C on. After I found the disconnected hose and fixed that. All the pods started working correctly and I neglected to re-check the vacuum. I just assumed since all were working as specified, then it was fine.

I do however clicking around the area of behind my PBU and switchover valves when I start the car and then sometimes at other times while driving so I suspect that I have another problem (I.E. PBU or faulty switchover valve)

Right now, however the vents are working as designed. I will now move on to replacing the A/C circuit so I can actually have cold air coming out!

I can tell you this, after being in there, and seeing that the pods are not all that hard to replace that the next time I do have a problem that I can isolate there, I will replace all of them and just be done with it.

I have also been trying to locate the switchover valves. Are they a dealer only item?

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----Adam

1985 300SD 322,000

A follow-up to my last post.

I have had a working system for a little while now but am still having one problem:

Most of the air that should be coming from the center vent comes out the defrost. I have replaced the defrost pod. It seems that it only moves the "short-throw" 20% and does not get the vacuum for the other 80% to fully pull closed.

The pod holds vacuum on both nipples. I am now leaning to the top switchover valve because sometimes the pod will pull closed, but most of the time it won't. It's a weird thing.

How does one test the switchover valve?

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----Adam

1985 300SD 322,000

When energized the switchover valves allow vacuum/air to flow. When de-energized the air passage is closed. Apply 12V/ground to the contacts and you should hear them click, then check for opening/closing.

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mjk

'84 300SD 119KMi (Liesl der Diesel)
'84 300D 326KMi when the oil left (former parts car)
'82 300SD 253KMi (new parts car)

I don't have the schematics handy at the moment but when I came across this problem it was due to a leaking center pod. This pod is exclusive to controlling the flow to the center vents.

Of all the pods, this one is the most difficult to service. It's located behind the pushbutton controller and requires a couple of hours, or more, to finagle everything. Do an advanced search for "center pod" and "SD Blue" and there are several posts where I've tried to explain some of the "tricks" I used to make it a little easier.

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Sam

84 300SD 350K+ miles ( Blue Belle )

The thing is, when testing for leaks from the switchover(changeover) valves only the first(top) one leaks down, but if I cycle between the buttons on the PBU sometimes it will work fine and not leak.

Right now with the glove box out I see the defrost pod pull slightly when the middle button is pressed. I pulled off the pod to check vacuum at the pod and it is good, then I pulled the lines coming from the changeover valve and checked them...fine.

The only thing I can think of is the changeover valve is leaking, or not opening fully allowing a vacuum on the long throw of the pod. But, it does work sometimes.

I just really want to find the faulty component so as to not throw money at it.



On the center pod, there is a relationship to the defrost pod. (see the attachment from user JUNKMAN above) I believe when the center pod is activated, it pulls the defrost pod on the "short throw" or ~20% closed, but am not sure of why yet.....still studying the FSM.

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----Adam

1985 300SD 322,000

I pulled the changeover valve #1 (top) that goes to the defrost pod (red/white). I did it without removing alot of things so it was a tight fit

I put an DMM on it and it read ~900 ohms, this seemed high to me and I didn't want to go to the trouble to check the other ones so I went to the junkyard.

Found one on a 500SEL and all six read ~42 ohms. I took them to my work where I have a DC power supply and checked them all at 11.5V and all clicked nice.

I swapped out my faulty one and put it on the power supply and got nothing. So, that changeover valve was bad.

For now I have fully functioning automatic climate control!

Will post again if this doesn't hold up long.

BTW I picked up all six of those for $10, they are worth grabbing on your next trip to the boneyard instead of paying $45 each ($270 total) new.

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----Adam

1985 300SD 322,000

Hi this is my first post I have a 420 sec 86
Please be patient am dyslexic and can not not write so well in englasa Google Translate

this is the first car I meck on so I'm noob in any way when it comes to this

Today when I install speakers in my car I could not find how I can remove the glovebox
and when I got off the panel below the glovebox the cabin air temp sensor fell down
the owner before me had MacGyver it but when it fell down, both wires broke of


So my question is on the sensor a got red and brown and the cable that goes there, I have 1 brown cable and 1 black/red/blue cable
What to what? brown 2 brown and black/red/blue cable 2 red ? or am I wrong

and where do I find the screws so I can remove the glovebox

ples help me