300CD Temp Control Regulator?
 

Anyone know where the Temperature Control Regulator is under the dash? It's not the CCU - been there, done that.

Would a faulty one explain fluctuations in the climate control, in spite of a new CCU installed?

http://img.eautopartscatalog.com/live/thumb/R202849489PRO.JPG

It's in the Fastlane system, and offered new and rebuilt. I never knew the 300Ds and CDs had these.

My rebuilt climate control unit works ok, but doesn't seem to have a middle ground between all the way on or off.

Any thoughts?

At the risk of being too simplistic, have you checked the tube that runs from the sensor to the temp regulator? The tube is supposed to be from the little vent in your dash to the regulator. Mine was completely disintegrated. This is a very common situation. You may have already made this fix. I, like so many others on this forum, replaced it with a piece of foam pipe insulation from the hardware store. I believe the foam insulation was for 1/2" pipe. I am a contractor and nearly always have some pieces of this around. It is handy for several uses. I believe the temp regulator or amplifier is behind the glove box. If you remove the glove box you will find both the tube and the temp regulator.

Hmmm..
 

You know, I replaced that temp sensor in the dash not that long ago (2 yrs), but didn't think to check the hose that it connects to. I never even had to take the dash apart, in fact.

Now that you mention it though, I noticed some bits and pieces of foam or maybe dried rubber in the process of removing the old sensor. I figured it was just old dash board material or something. That hose might very well be toast by now.

This is worth a look, thanks.

I take it you never had to mess with the regulator itself, then?

No, my regulator seems fine. I have replaced that tube and the pushbutton unit at different times. I have, of course, rebuilt the monovalve. Hasn't everyone? Some people have several times according to postings on this forum. If your tube is disintegrated as mine was, I doubt you will be able to regulate temperature. It is a very easy fix. Good luck!

When I got mine it had a piece of clear rubber hose in place of the OEM foam. This worked but would absorb dash heat badly, so I insulated the rubber hose. Seems a little more sturdy now.