W123 Monovalve disassembly and troubleshooting - Page 3 - PeachParts Mercedes-Benz Forum

vwnate1 · #31 11-18-2016, 11:45 PM

I can't see which one is assembled wrong......

I have occasional vanishing heat in my '84 300CD so I'm curious if I re assembled it incorrectly .

funola · #32 11-19-2016, 10:27 AM

The black spacer under circlip in pic is correct.

funola · #33 11-19-2016, 12:46 PM

Updated drawing with more annotation.

funola · #34 11-19-2016, 01:15 PM

Quote:

Originally Posted by Demothen

Funola,
Here's some pictures of my spare monovalve in both configurations (incorrectly assembled and correctly assembled) with some measurements taken. This is all spare parts (thus the torn diaphragm - and i'm out of snap rings). I'll explain the pictures a bit later, short on time right now but I wanted to get them uploaded.

I do not see the circlip installed in your pics. Is that an optical illusion?

Demothen · #35 11-19-2016, 01:40 PM

No, thats a spare unit and i am out of snap rings/circlips

funola · #36 11-19-2016, 03:12 PM

Quote:

Originally Posted by Demothen

No, thats a spare unit and i am out of snap rings/circlips

Each core should have come with its own circlip. Did you lose it?

vwnate1 · #37 11-20-2016, 12:21 AM

THANK YOU ! .

Now I have to go get caught up on my works and drag my neglected Coupe out of SWMBO's garage and take the Monovalve apart to see.....

Sheesh ~ so many old vehicles, so little time !

.

Demothen · #38 11-20-2016, 04:03 PM

Yes, those snaprings have a habit of flying across my garage

Demothen · #39 11-20-2016, 05:06 PM

Okay. So in the first picture I uploaded on Friday, you can just barely see the spacer is located behind the plunger. This is how I had it in the car when it was not functional (again with an intact diaphram and a snap ring installed). Picture two shows the distance from the end of the plunger to the flange in this setup (approx 20mm). Lets call this config A.

Picture 3 shows the shim in the correct location and the distance to the tip of the plunger is shorter (17mm). Picture 4 shows the thickness of the shim (about 3mm). This will be config B - or the correct assembly.

So lets assume that the total distance before the plunger seals against the housing is 30mm (I didn't measure this unfortunately). In config A (incorrect) the plunger has to travel 10mm to seal. In config B the plunger has 13mm of travel. Now the important thing here is that this sort of solenoid won't have a linear amount of force as it travels throughout it's stroke. Since the steel weight will get closer to the magnetic coil the further it travels, it will experience a stronger activation force. Not sure if this is a second or third power function, but that isnt really important. By restricting the stroke of the plunger, I think I made it easier to open by water pressure

funola · #40 11-20-2016, 06:08 PM

I am not even going to give my opinion on the effect of having the spacer in the wrong place since that is an invalid configuration. Since this is a monovalve troubleshooting thread, let's trouble shoot a correctly configured monovalve.

Have you looked over the updated drawing? Is it correct?

What was your original problem which led you to suspect the monovalve?

funola · #41 11-20-2016, 06:12 PM

Quote:

Originally Posted by Demothen

Yes, those snaprings have a habit of flying across my garage

Tip: Work inside a clear plastic bag next time you r&r the circlip, or put a piece of duct tape half way around the circlip so it can't fly off.

Take pics before taking things apart so you can put it back together correctly

Demothen · #42 11-21-2016, 12:44 PM

Oroginal monovalve when i got the car had a torn diaphragm, its been 2 years but I think it was shutting off the heat at high rpms. And i realize that was the incoreect configuration, but its good to have some idea how the unit actually behaves for people who read this later on, in case someone runs into a similar problem. Its going to be at least a couple weeks until I get the car back on the road to fully test it.