We've all read the options regarding the monovalve but I stumbled across this today.

Klima Design Works | Monovalve and Coolant Circulator Pump Eliminator / Upgrade Kit

They're using a vacuum operated valve. Thought it was a cool idea.

__________________
--------------------------------------------
Old Blue - 83 240D 6 speed manual trans, OM648
Green Machine - 2001 Europa G500
87 300SDL Bought on Peachparts. Low-ish miles..?

Family Truckster - 2012 VW Touareg TDI

Patchouli Wagon - 2004 E500 - SOLD
333k mile 97 BMW 750il V12. - SOLD
The Californian - 85 300TD - SOLD
Daily Super Sedan - 03 Audi S8 -SOLD

I can't access that site. I wonder if it is proportional control (i.e. "servo"), or just on/off. I don't know if the M-B controls it proportionally, or if it really matters. I am sure on/off would work. One guy here installed a later (W124?) mono-valve in the area where the silly & unneeded "aux water pump" sits. He did have to extend the cable.

__________________
1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans

it contents include:

OE type Pierburg vacuum solenoid made in Germany.
Durable, high flow vacuum controlled heater valve with external control arm for verification of operation and long life.
OE style semi-rigid polyamide vacuum supply and vent lines.
All necessary vacuum elbows, soft vacuum hose, and vacuum tees for conversion.
New heater hose for associated components.
Genuine Mercedes electrical connector and terminals for electrical connection.
Detailed installation instructions.

Looks interesting, I just replaced my monovalve with MB parts, works great, but I know it will fail again. maybe this would work, who's going to test it?

Thats how the W201 climate control is setup from the factory and it works pretty damn well.

__________________
CENSORED due to not family friendly words

Bumping this thread.

I noticed a coolant leak at the monovalve assembly. It's not gushing, but enough to have drained the reservoir within a few weeks. Having gotten tired of screwing with the monovalve, and showing signs of a faulty aux pump, I decided to purchase this product.

I've just ordered it tonight and intend to install as soon as it arrives. Will update with thoughts after it's in.

Really? So the parts for this kit could be scavanged at the pick-n-pull? Which model 201's use this?

__________________
Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

Back to the future with this bump for the results.

I went with this Monovalve Eliminator kit and like it.

On the highway my heat would get cold, monovalve was getting shut off by the water flow/pressure at higher RPM. I’ve heard the cheap aftermarket monovalve inserts are totally useless. Instead of purchasing the expensive dealer monovalve insert or going with a complete new monovalve assembly from different car and adapting it I decided to go with the Klima Design Works setup for the same or less money.
They were great to deal with. I initially had a problem with the vacuum not releasing and heat staying on. They immediately responded and told me how to fix (pierce rubber bleed off orifice with pin, it had self sealed).

I also sent the three components; silver CC brain, push button unit and black blower control box (along with my cruise control) to JamesDean for a rebuild. Climate control (and cruise) now works as it should. The heat does modulate to keep the interior where the temp wheel is set but it is not as smooth as a fully manual system. I greatly prefer a manual system that I can set myself. I envy those that have the simple heat/AC in W123's!