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the what???
 

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If you are talking about the heater mono-valve, I don't believe 190s have them. There is a heater valve, however, located on the passenger side of the car, underneath the windshield cowl.
 

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Discussion Starter #4
RE: Mono-valve

I keep reading about the mono-valve and how it is effecting the heat and ac functions. My unit blows hot air from side and defrost vents and cold air from the center vents. It is also stuck in the max position, my control switch moves but doesn't adjust amount of air flow. I have no problem changing things to fix the problem, just a place to get started.
 

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There is no mono valve in the 190E. My 560SEL has one and when it fails you get NO HEAT.
In your case (190E), the problem is a vacuum leak at the heat controller. The center vents will always blow outside cold air. Your side vents are the ones controlled with your temperature adjustment. I have the same exact problem but I manage it by selecting the heat vent setting to blow in the foot well and that somehow allows the controller to regulate the temperature to what I want.
 

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Heat control valve is located forward of the glove box, forward of fireshield, under the leaf guard below the windshield. Vacuum is used to close. Test with vacuum pump. With applied vacuum the lever will slowley move to the closed position. Remove vacuum, lever will spring back. Pipes and hose to and from will be hot if car warmed up to operating temperature.

I have seen pics where someone has installed a shutoff to close the valve manually, valve is only $20 or so. Vac leaks are hard to find.
 

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fyi the center vent is always cold/outside air.
 

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Discussion Starter #9
Thank you all. This is my first old Mercedes project, I won't touch anything on my new S or ML. I also hope I'm following forum decorum.
 
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