Would you like to reveal the manufacturer's name?

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When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.

I don't know the manufacturers name. It was a few months ago and I don't have the box now. But, I did remove the eclip and plunger. The heater works fine now. But, I'll need to get a functioning mono valve before spring since I use my A/C in the summer.

Now, with the mono valve plunger removed there seems to be a small coolant leak in the area of the mono valve. But, it doesn't appear to be the mono valve itself since it is constantly dry. There is a constant plume of steam coming from the area right under the mono valve while running. Maybe the hoses connecting to the mono valve. Just not sure why it started leaking right when I removed the plunger from inside the mono valve.

If the diaphragm was intact and came off with the plunger, you won't have a leak-tight seal.

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When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.

You're right Tangofax, Does anyone know of a manual valve that can replace this mono valve? I only need to switch form heat to A/C a few times a year.

If you just procure a genuine MB insert, you will probably be in tall cotton. There are plenty of reports of the aftermarket versions causing the exact problem that you report.

https://www.pelicanparts.com/cgi-bin/ksearch/pel_search_2016.cgi?command=DWsearch&LastVisited_input=3303&Previous_Section=VENTAC&make=MBZ&description=mono+valve

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When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.

It's truly mindblowing the lengths people will go to avoid buying a cheap part that will fix their problem and last for another 20 years. Buy the d*** OE cartridge and be done with it.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

I just ordered the OEM part. In the mean time, I have a plastic Lasko elbow that I bought at Home Depot. That is actually working better that the mono valve as long as I want heat and not A/C. In fact, if your A/C is not working, just take out the mono valve and use this elbow as a permanent fix.

It’s ironic that this subject has appeared on here this week. I had a similar problem with my ‘87 SDL where I had no heat at speed, but I had moderately warm “heat” at idle. I unplugged the Monovalve in hopes that I would have full heat all the time. No such luck! It still produced the same results. I then removed the Monovalve. It was revealed that the diaphragm was torn. I experimented with using a sealer (Gorilla Glue brand super glue) to repair the diaphragm and reinstalled the Monovalve back into its spot. IT WORKED!!! It worked well for about a week and then the diaphragm ripped just where it meets the metal center. At this point it was back to doing the same thing as before. I then removed the plunger to have full heat for the time being. I purchased a new Monovalve insert from a Parts supplier I deal with on a regular basis. I knew that MTC was NOT a wise choice, but I decided to try it. I installed it last night only for my family and I to freeze miserably this morning as we started out on a 2.5 hour drive. After 10 miles of extreme cold I pulled over at a truck stop and removed the Monovalve and took off the plunger. HEAT!!! Full heat, for the duration of the day.

A little while ago I took my Fluke multimeter and tested the plug. There’s 12v on one side constantly, regardless of any setting on the CCU. I’m not sure if that’s how it’s supposed to be (I hate automotive electronics!). Anyway, I’ve ordered a “genuine Mercedes” Monovalve insert from the sponsors of this forum and I hope it will make a difference. In the morning I’m also going to transfer the plunger from the MTC junk to my original OEM Monovalve insert and see if that may work. It’s too cold to be driving around without heat. Too cold for me anyway. I’m tender.

That is as it should be. The monovalve is controlled by switching the ground side of the circuit, either by the temp control setting (extreme limits only) or by the electronic temp control module.

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When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.

Plastic? Lasko? That might not last very long, and could blow an engine when it fails.

I'm pretty cheap an all but, there's no way...

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1985 300TD 1981 Scirocco 1.6D conv 1986 Golf 1.6D 2003 Golf TDI

Thanks. So, one side should be constant 12v and I’m assuming that the other side will vary in it’s voltage as the temp dial is moved, correct?

One side will be 12V, the other side will be switched to ground on and off, it is not variable. The CCU will pulse the valve on and off to maintain a desired temperature of the heater core.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

I took the new diaphragm from the MTC unit and installed it on the OEM (Bosch) unit and now I have heat on demand. I also have cool air on demand as well as moderately warm/cool air on demand. I’ve unplugged my auxiliary water pump because it is no good. I removed it and connected 12v to it and couldn’t get the motor to budge. I also disassembled it for cleaning. The motor moves freely, but it doesn’t work when given 12v. It’s reinstalled just to keep the stock plumbing for now. I will replace it...eventually. It’s definitely not a pressing matter.

If you decide to delete the Aux pump, replace it with a 90˚ brass elbow. The vanes in the pump block coolant flow to an extent, with the pump removed and a 90˚ elbow inserted in its place, my SDL heats nearly as good as with the Aux pump running. Certainly no issue making the cabin too hot to tolerate.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Got my new mono valve cartridge. Now I can't find the two washers that go in there in addition to the warped expansion washer. I couldn't find the washer on Pelican Parts. Does anyone know where to get those two washers?