Ok, so I'm trying to get through the checklist on my 1985 380SE Diesel (converted) before winter, yes I know I have lots of time, but I want to make sure I get the Heat fixed before winter. I'd also like to fix the A/C but figure thats a waste of time until the rest of the system functions correctly. So without further adieu, the issue at hand.

Symptoms:
1. Blower will not start unless Bi-level, or Defrost are selected first. After one of them has been pushed the other two setting will work, as will the automatic and hi\low settings.
2. regardless of the setting selected, none of the vents change. Seems the vents will not change from the defrost setting.
3. Temp wheel functions as it should and blower speeds up and slows down in relation to its position. I have noticed that after full heat it doesn't like to go full cold. Thinking this ties into symptom 2 and guessing that the heat flap isn't closing.

Actions taken so far:
1. CCU unit first re-soldered, and then changed out with a unit from the wreckers with no change in symptoms.
2. Mono valve replaced with good unit from the wreckers. Thats how I got heat.

Also finally got around to testing all the lines to the pods, and I'm a little worried... from top to bottom of distribution valves, as numbered on the bracket that holds them
1: holds at 20inhg
2: Bleeds quickly down to 10inhg and holds
3: can only pump up to 5inhg and then drops to ~2-3 and holds
4: holds at 20inhg
5: Bleeds quickly to 0
6: bleeds slowly to 4inhg and then holds

The FSM isn't all that easy to understand so I'm not quite sure what they should hold. I figure number 5 is shot but what about the others?
So thats where I stand. Basically I need some further guidance and some good instructions. Both I'm sure will come my way with abundance from here.
-Thanks, Dude99

It's over my head, but one thing you might want to try when it comes to electrical problems, is changing the fuses if you haven't done so already.

The ones I have on my car, W124 1991 300d, they're the aluminum ones and they pit over time, and can cause problems.

I replaced mine with the newer copper ones.

Good luck.

bump

I know I'm mixing apples with lemons here, systems-wise, but I had just about precisely the same issues on my '79 300sd at one point and the cure was changing the pushbutton panel.

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

I've already tried that. Like I said in my first post. Sadly it made no difference.....

Top to bottom sequence is:
Defrost
Footwell
Center Flap
Diverter
Fresh/Recirc

You have several pods that need repair or replacing. Of course, checking the pod directly would be best before replacement, in case there is something else awry. On the W126, most are fairly accessible except for the center flap pod. The pods that drop quickly, yet hold at a very low vacuum, are probably leaking as well. They sometimes hold a little bit if the diaphragm has a very minor leak. From your description, the pods that leak are located behind the glove box and in the center console, behind the pushbutton controller. There was someone who sold the diaphragms for the short throw pods but it has changed ownership so you will need to search, here on the forum, and find out the latest source. I'm not sure about the Int'l shipping.

For the center pod:
To remove it you will need to pull the ACC controller and center vents. Also, removing the glove box liner is good spot for some light. It is a good idea to plug the lower area with some rags or something because parts can disappear into the great black hole.

Remove a couple of the plugs and the rubber flex ducting away from the right side of the center vents. To remove the pod itself, there is a small portion of the plenum that is attached with very small screws behind it. Once they are removed,(long 1/4 dr. wobble ext.) you can pull the pod and mounting out enough to see the actuator rod. Push the rod to the left and it should pop out of the clip. (this clip is the same type as the one on the top right side of the plenum for the defrost actuator rod)

Once you've rebuilt the pod, I found that some light wire, looped through a small hole on the flap, and some hemostats held the flap down in order to reinsert the actuator rod.

It is a bear because you have to see what you are doing, insert several tools and work in an area about the size of a wall outlet.
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Sam

84 300SD 350K+ miles ( Blue Belle )

Here is a pic taken from drivers seat of my 85SD. Pods at top right are behind glove box. I've forgotten the details but other pods are left of center behind the box holding heater core etc. Only the pods accessible without pulling dash were leaking. The dash was out because I found a beautiful one in an 89SE.

Attached Thumbnails

 

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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.

A similar account from my 300D:

I'm having the same problem with having to "jump start" the fan by engaging the bi-level then switching over. My theory is that one of the relays on the CCU board needs to have its contacts cleaned... just haven't had the time to frak with it.

I ended up completely disabling my center flap and diverter actuators due to leaks. Center flap doesn't bother me because I want it blowing air all the time. I tried to repair the diverter actuator diaphragm with a bit of a bicycle inner tube patch. It held for about 2 weeks. The patch held, but it split again in another area. Dunno what to do next... I'd rather repair it than replace the whole actuator.

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1991 300D 2.5 "Rocinante"
2002 Golf TDI "Teen Spirit"
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1984 300D
1966 Mustang I6 3sp
1985 Mazda RX-7 GSLSE
1982 Toyota Supra
1977 Datsun 280z
1971 Datsun 240z

Well I guess I just hit the wreckers with a Mitty vac and start hoarding actuaries untill I find a set that work. Thanks for the help.

@ Bengoshi2000
I thought it was the relay on the CCU as well but I swapped it out with a second one and the exact same symptoms persisted. I seem to remember reading somewhere (maybe in the FSM) that certain systems (possible the blower) are triggered when certain flaps open. So I'm going to replace the vacuum pods and see if that remedies the blower problem.