SD climate quandary

[Hit Man X]

I am still fooling with trying to figure out why I have no low speed from my fan, but that is not the purpose of this thread.

When I flip the system on heat (any of the settings minus Off), I still have air leaking out of the center vents to my face. I failed to make notes, but seems to me this air was cool not hot. I have hot air to my legs/feet and out of Defrost if selected.

Does anyone know which pod could be leaking, if that is what is my problem? I really do not feel like pulling the dash out a few times to test all the pods then to do it again once the pod arrives. I have replaced the three main, double throw units and am basically to the point where I am going to just replace these other four and eliminate that variable all together.

So that leaves these:

Central Hot Air Flap Control (000 800 67 75)
Air Scoop Flap Actuation (000 800 40 75)
Operating Unit to Defroster Nozzle Flap (126 800 14 75, black rectangular)
Legroom Flap (000 800 42 75)



What about those Vacuum Change Over Valves (000 800 04 78)?

[JamesDean]

Pods in 126.120 as per Mercedes EPC

[4thesporty]

R/ the changeover valves. I had to R/R one (defrost) a while ago.

They are easy to pull and bench test with a 12V power supply, or battery. They can also be had very cheap in the JY, and of course bench tested before install.

Do you sometimes get a rapid click sound coming from the changeover valve area? That is what happened to mine, it usually did it when I first turned on the ACC,

[Hit Man X]

What issues were you having that lead you to the change over valves?

I assume the 12V to it allows it to click like a nitrous solenoid?

[JamesDean]

[Brian Carlton]

Originally Posted by Hit Man X

What issues were you having that lead you to the change over valves?

I assume the 12V to it allows it to click like a nitrous solenoid?

The thing to do is to perform some tests with a Mityvac.

You do this by exposing the set of changover valves where you can access all the pods via vacuum lines.

The changeover valves are sitting just to the right of the CCU. You access them by removing the carpet and kickpanel on the right side and pulling the piece off the transmission tunnel. It will just barely slip out of the console.

You can unscrew the manifold with all the valves attached for easy access.

Now you can attempt to pump up each pod and see if it operates properly (holds vacuum). You can also test the changeover valves if you T into the output line (run the engine and the CCU to do it).

Why guess when an hour's worth of testing will tell you what you have.

And, there is something unique about the center vents. I had put vacuum to the center vents all the time and chose to regulate the vents via the console controls. Bad move. Those vents will never provide full heated air. They get air from a point before the heat exchanger, apparently, because they will freeze you out in the winter, even with the dash controls closed.

[Hit Man X]

not what I wanted to hear Brian, but it does make the most sense to avoid wasting time and spending money frivolously.



Back to testing tomorrow or Monday... will report back with findings.