W126 Erratic heat due to a faulty mono valve

How to fix the mono valve on W126 S class Benz. That is the same part used in many older Benzes of the 1980s. US version is a mono valve, and the rest of the world typically had a dual zone duo valve.

The following genuine BMW mono valve insert is identical to the Benz part A0008350644: Genuine BMW E24 E28 E32 E34 Mono Valve Heater Solenoid Valve OEM part number 64118390132. It costs a pretty Penny, but this has a greater chance fixing your erratic heat issues than buying the cheap online parts store inserts. Update: Sadly this part is no longer available.

Update: In the event you have a genuine mono valve that no longer works, there is now a repair kit that helps you replace the rubber parts. Here is the link: https://www.pelicanparts.com/More_Inf...