The heat is stuck on in my 1985 190e. I checked here in the forum and found that it is usually caused by the monovalve. Since I have the MB CDROM manual for this car, I looked it up on there too. I read that the valve is closed when there is vacuum to it, which leads me to believe that I either do not have vacuum to it or that there is a leak in the valve. Am I correct in thinking that vacuum to this valve simply operates a plunger type device? If so, since it is like 90 degrees here, can I do something to force the valve shut manually while I await the arrival of the parts to correctly fix it? It appears that while this valve is open, the AC compressor will not engage.. is that correct? Thanks in advance for help with this.

I would not try to cheat the valve for a temporary repair if it is bad and won't respond to changing signals. Simply find a way to block flow in the hose. These formed hoses aren't cheap so don't ruin a hose by clamping it for a long period of time. Remove the hose while cool and put something inside that will fit up in the hose to block flow then reconnect it so nothing spills out from either side.

Remember THIS IS A TEMPORARY REPAIR!

Good luck,