Hi Lea,

I did the "Destructive Testing" shortly following the tests I described in post #71.

Destructive Testing may not be an appropriate description. I really was not testing anything. I just did it to fulfill my curiosity.

My wife caught me in the kitchen -where she is the ruler-, and refused to donate her pots for this worthy cause. I then took the components down to my Garage, -where I am the ruler- and basically broke them apart.

Jim, If I remember correctly, somewhere on your Web site you mention that you have a contact at "Sachs", and that you have spoken to them before. If so, perhaps you can get in touch with them and ask the appropriate person to join this debate and hopfully to clarify the design intention for their Fan Clutch.

Regards,

Phil

Here's some answer to your questions. .
 

From what I can see, the differences between the bms seem to be;
1) BMS: mine is marked "TB 1577A - GE"; yours "?? -TB1577". Note the differences including 'spaces'.
2) Different mat'ls: mine is definitely brass and steel because top side appears a 'goldish' color; yours is ? But the TOP layer is NOT brass. Looks exactly like the BongC36 "tropics" VFC. It's appears to be the SAME material.

Good bit of business! Again, your bms is a 'rare' bird, so don't loose it.

Mercedes' Technical document No: 20-3100 Titled "Temperature Controlled Viscous Fan Clutch" states the following:

"A second (internal) bimetal switches off the fan in a smooth operation in the upper speed range above 4,500 RPM depending on the ambient temperature"

So there does seem to be a second bimetal inside the clutch unit itself. I should mention that subject document applies specifically to the 124 Body. I don't have access to the technical documentation of other models, but it may well be that all VFCs have a second internal bimetal.

Phil

Jim

Thanks for your comments and especially detailing your answers concisely.

?? Do you mean 100C ?? Have you a picture so we can try and 'see' the movement required?

You talk of engage, but what are you referring to exactly? Remember I haven't actually carried out the test for myself yet so excuse me if I do not follow you.

I would like to know how much movement was measured between ambient and 90C as if we're talking of 1.78mm I doubt one can see this underwater. Maybe Phil has a superior measuring technique?


And of course there's my unit which also operates as expected and also has EXACTLY the SAME part number as tested by yourself. So, one may think Phil's a lier (no accusation meant here Phil) but two of us who say their VFCs work correctly - are we both liers? That's the whole reason for this debate - or at least why myself and Phil are debating. Trying to resolve the differences between why both our units operate within spec but yours do not.

My apologies, an incorrect statement, although some on this thread may have perceived this. I stand corrected.

This is a little unfair don't you think. The documentation I specifically referred to was internal MB data, which is provided to MB franchises only. It was for the 129 and 140 model only and my generalisation based on this info. was that a VFC is designed to lock BEFORE the aux fan, and that stands for the majority of vehicles with VFCs of similar construction to ours (non-electromagnetic) - whether you believe it or not!

From the MB data posted by Phil (post45):

Right - now to try and track down the differences:

I find it difficult to believe MB doesn't distinguish individual parts by individual part numbers. Working in a manufacturing and design environment we cannot have two different parts with the same part number, this is industry standard (apart from 'Lead Free' electronic components and that's all getting way out of hand). So the only way to distinguish the tropical unit is by missing out a dash? :confused:

Now my car's data card shows UK as it's destination - why would MB fit a 'tropical' VFC to mine. Have you ever visited the UK, it's hardly tropical :sun_smile


One last point:

The bms you originally detailed on your own web site clearly refers to the
[S] see Menu 18! :eek: ;)

I'm off to read that 'tropical' thread again.... to see if I can gleam any further info...

Jim,

Knowing that there are 2 bms', (at least for my model), an EXTERNAL bms that engages the Fan above a certain air temperature, and an INTERNAL bms that disengages the fan above a certain rpm AND air temperature, could help clarify things a bit.

I will assume for now, rightly, or wrongly, that under certain circumstances, a vfc can fail in such a manner, that the mechanism associated with the INTERNAL bms stops operating as designed. This will cause the fan to either DISENGAGE at a much lower rpm then intended, or to remain disengaged, even though the external bms, and its associated mechanism work as originally intended.

An INTERNAL bms mechanism failure, could account for at least some of the vfc failures that you are reporting.

Phil

Phil

Why a second bms - surely the cut-off point is determined by rpm, not temperature. I have an internal drawing of the VFC fitted to the 120.980 engine and there's a spring clearly visible. I suspect this spring is responsible for the cut-off not a further bms wouldn't you?

Lea,

I am not sure at this point how the second bms functions. I now wish that I would have kept my original vfc. In any event, I attached the Mercedes pdf document that I was referring to in my earlier post today (Post No 122). That's the one that talks about the second bms and its function.

I need to think this through a bit more, perhaps there is also correlation here that could explain the discrepancies in the observations between Jim's tests and my tests.

Also for anyone reading this please keep in mind that the attached pdf is for the W124 Models, and may, or may not be applicable to other models.

Regards,

Phil

Where's the attach image icon/button gone - I'm sure I used to scroll down and hit a button.

Perhaps I'm loosing it tonight - must be due to having my first meal since the upset stomock...


Ah, silly boy, I must have hit the little arrow which detracts the 'Additional Options'... LOL..


Here's the piccy on the internals of the 120 - I'll go and check to see if it's listed against our models...

Hi Lea,

I just took a look at the drawing of my own fan clutch as detailed in Mercedes document 20-310. (I can't attach it, the pdf file is too large)

But neither the document, nor the associated diagram make any reference to a second internal bms. The only reference to a second internal bms that I found was in document 20-3100 that I just posted.

Phil

Phil

If you want to attach something which originally fits on a single screen, easiest way is to hit the 'Print Screen' button, then paste into a paint program so you can save as a jpg. Choose at least 30% on the jpg options when saving.

Lea

Lea,

I am running under Mac OS. so I don't have a print screen button as such. There is a way to do it from within the Mac OS, however I can't remember how

In the interim if you want me to E-mail you a copy of the pdf please let me know by private message. I'll need your E-mail address.

Regards,

Phil

Hi Phil

I was just wondering if you can see the same spring on your VFC as in the 120 diagram that I attached earlier - other than that I'll take your word ;) :)

In Acrobat (pdf reader) there is a graphics select tool, next to the text select tool...
You can usually copy and paste about ¾ of a page into a graphics application and save it as a jpeg of the correct size to upload.

I had been watching this thread... which seems to need it's own tech support section... to see when and where the duel would be set... You fellows seem to be getting somewhere though... keep up the good work. ;)

Hi Lea,

Here is an attachment ,(in MS Word Format) from the Mercedes document that shows the details of my fan clutch. Hope you can open it

Regards

Phil

Hi Lea,

Here is an attachment ,(in MS Word Format) from the Mercedes document that shows the details of my fan clutch. Hope you can open it

Regards

Phil