Some of you may have found out about this first part some time ago. Since the
monovalve insert neoprene diaphragm seems to crack/tear on a regular basis of
between 3-5 years, I contacted a representative at Robert Bosch to see if the
neoprene parts associated with the monovalve insert are available separately .
. . the short answer, no.
The reason I was interested in this is that I replaced the monovalve insert
shortly after I purchased my '84 300D turbodiesel in '96, again in 2001, and I
had to replace it again just recently. Of the three washers sitting on top of
the monovalve insert shaft, I had lost the 1st one in '96 but all seemed to
work OK with just the wavy steel washer and the wide, thick washer on top.
When I recently replaced the monovalve insert, I found a thin washer to place
on 1st and on top of this placed the wavy steel washer and a wide thick
stainless washer. The top seemed to sit on flush with the monovalve housing
prior to installing/tightening the four screws. Results - heat only in defrost
mode, all other settings heat would disppear suggesting 1) There was either a
crack/tear in the new monovalve insert I installed, or 2) Something in the
overly complex electrical part of this lousy ACC system went south. I have
trouble believing #2 as it would be too conincidental. I opened up the
monovalve again and inspected the new monovalve neoprene diaphragm I installed
and found no cracks/tears. I replaced the top wide thick stainless washer with
the original wide thick steel washer and the top plate does not sit flush with
the monovalve housing prior to tightening the four screws but, after tightening
the four screws, there doesn't appear to be any leaks at the monovalve housing
after starting the engine and operating the ACC on either defrost or off. If
this works and I've got my regulated heat back, I'll report back. Otherwise,
if someone out there has a clue please let me know what may have gone wrong.
I'm hoping that one of these days I may actuallty understand this lousy system.
TIA.
G. M. Brown
Rochester, NY
