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  #1  
Old 12-25-2009, 06:44 PM
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Can I disconnect Windshield Heater ?

I have to replace the heater hose that goes from drivers side of cylinder head at rear to heater core.

My 1983 300SD has that little stub that feeds what is described as a windshield heater.

I ordered the wrong hose and am wondering what will happen if I leave
the stub to windshield heater unconnected.

Where I live it goes into the 20's. Don't really know what they mean by "windshield heater".

So two questions what does this actually heat and can I use
the hose that has no stub. (cheaper too, that hose with stub is 3 to 4 times the cost).
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  #2  
Old 12-25-2009, 07:18 PM
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Quote:
Originally Posted by rhodes2010 View Post
I have to replace the heater hose that goes from drivers side of cylinder head at rear to heater core.

My 1983 300SD has that little stub that feeds what is described as a windshield heater.

I ordered the wrong hose and am wondering what will happen if I leave
the stub to windshield heater unconnected.

Where I live it goes into the 20's. Don't really know what they mean by "windshield heater".

So two questions what does this actually heat and can I use
the hose that has no stub. (cheaper too, that hose with stub is 3 to 4 times the cost).
on the w126, i don't think it has a front windsheild heater. only the rear is heated, and that by an element that runs the length of the windshield, which is heated by an element that goes up the back side of the c-pillar.

whatever it is that's attached to the heater core, it's not to heat the front windsheild
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  #3  
Old 12-25-2009, 08:27 PM
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On 126 chassis vehicles there is a coolant heated heat exchanger inside of the lower windshield, this warms the lowest part of the windshield preventing an accumulation of snow or ice that is swept there by the wiper motion.

It can be disconnected without too much of a problem, the only issue would be to close or plug both the coolant feed and return lines to prevent the loss of coolant. There is a thermostatically controlled valve which controls the coolant flow into the heat exchanger. This valve and the associated hoses are located beneath the cowling which also covers the wiper transmission.

You can disconnect the small inlet hose from the heat exchanger and loop it back onto the return pipe bypassing the heat exchanger completely.

In your case it sounds like you will need to get in there and plug the return line so as to prevent coolant loss from it and the new incorrect line without a heat exchanger inlet opening doesn't need any sort of plugging.
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  #4  
Old 12-26-2009, 01:21 AM
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Correct

Quote:
Originally Posted by Billybob View Post
On 126 chassis vehicles there is a coolant heated heat exchanger inside of the lower windshield, this warms the lowest part of the windshield preventing an accumulation of snow or ice that is swept there by the wiper motion.

It can be disconnected without too much of a problem, the only issue would be to close or plug both the coolant feed and return lines to prevent the loss of coolant. There is a thermostatically controlled valve which controls the coolant flow into the heat exchanger. This valve and the associated hoses are located beneath the cowling which also covers the wiper transmission.

You can disconnect the small inlet hose from the heat exchanger and loop it back onto the return pipe bypassing the heat exchanger completely.

In your case it sounds like you will need to get in there and plug the return line so as to prevent coolant loss from it and the new incorrect line without a heat exchanger inlet opening doesn't need any sort of plugging.
The heater was added during R&D to keep the wiper blades from freezing down in cold weather.



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  #5  
Old 12-26-2009, 01:24 AM
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the heater valve is not located under the cowl--it's located in front of the cowl behind the firewall. you can replace the w126 style heater valve with the w123 style, which doesn't have as many openings for hoses, and then just fold over the unused hoses, and use the hose clamps to clamp them shut
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  #6  
Old 12-26-2009, 02:09 AM
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Quote:
Originally Posted by Sev View Post
the heater valve is not located under the cowl--it's located in front of the cowl behind the firewall. you can replace the w126 style heater valve with the w123 style, which doesn't have as many openings for hoses, and then just fold over the unused hoses, and use the hose clamps to clamp them shut
The "valve" in question is not the "heater valve" more commonly referred to as the mono valve. The heat exchanger valve; that controls the flow of coolant to the windshield heater you didn't even know existed, is located under the cowl as I've described. It is thermostatically controlled by a wax pellet which reacts to ambient temperatures keeping the valve closed when ambient temps are above freezing and opening the valve when ambient temps get low enough.

Obviously playing the fool is a part you relish; but being a fool is another matter, it's often better to keep quiet and let people think you are a fool than to speak up and remove all doubt!


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Last edited by Brian Carlton; 12-26-2009 at 10:25 AM.
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  #7  
Old 12-26-2009, 02:13 AM
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Enough

Quote:
Originally Posted by Sev View Post
the heater valve is not located under the cowl--it's located in front of the cowl behind the firewall. you can replace the w126 style heater valve with the w123 style, which doesn't have as many openings for hoses, and then just fold over the unused hoses, and use the hose clamps to clamp them shut
Wrong three times..
Please stop.
A slow correct answer beats all wrong answers.

* The W126 does have a windshield heater.

* His issue can be quickly resolved by plugging the coolant feed hose from the mono-valve where it is attached to the thermo-valve MB# 126 830 04 84. First attached picture.

Fastlane: thermo-valve
http://catalog.peachparts.com/item.wws?sku=1268300484

Changing the mono-valve as you suggest, would reduce the heater core flow 50%, directly impact heater performance, and NOT fix his issue. Second attached picture.

The correct mono-valve unit is MB# 000 830 37 84 Third attached picture.

Fastlane: mono-valve unit
http://catalog.peachparts.com/item.wws?sku=W0133-1600853



The W123 unit is MB# 000 830 29 84 Fourth attached picture.
No longer available NEW...
Attached Thumbnails
Can I disconnect Windshield Heater ?-1268300484.jpg   Can I disconnect Windshield Heater ?-w126-heater-core.jpg   Can I disconnect Windshield Heater ?-0008303784.jpg   Can I disconnect Windshield Heater ?-0008302984.jpg  

Last edited by whunter; 06-07-2011 at 04:29 PM.
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  #8  
Old 12-26-2009, 02:19 AM
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i have no problem being wrong--i just don't like being called a fool when i make a mistake...
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  #9  
Old 12-26-2009, 02:25 AM
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Quote:
Originally Posted by whunter View Post
* His issue can be quickly resolved by plugging the coolant feed hose from the mono-valve where it is attached to the thermo-valve MB# 126 830 04 84.
I'm pretty sure in addition to this, the OP would also need to plug the other hose to/from the heat exchanger otherwise coolant would flow back thru that hose, thru the heat exchanger, and out of its inlet, back thru the thermo valve when and if it is opened or leaks and finally drain out of the system thru the hose from the thermo valve which normally attaches to the small bib on the mono valve. I don't think plugging only one hose of the two connected to the heat exchanger will keep the system sealed up.
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  #10  
Old 12-26-2009, 03:13 AM
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Hmmm

Quote:
Originally Posted by Billybob View Post
I'm pretty sure in addition to this, the OP would also need to plug the other hose to/from the heat exchanger otherwise coolant would flow back through that hose, through the heat exchanger, and out of its inlet, back through the thermo valve when and if it is opened or leaks and finally drain out of the system through the hose from the thermo valve which normally attach's to the small bib on the mono valve. I don't think plugging only one hose of the two connected to the heat exchanger will keep the system sealed up.
No.
His issue is that the wrong hose was ordered.
He got a straight hose = Two opening MB# 126 832 20 94.
The small steel windshield coolant return tube will be open.
The tube could be capped, however, it is easier to find/make a plug for the feed hose to the thermo-valve.

He needs MB# 126 832 30 94 ONLY FOR USE WITH WINDSHIELD HEATER = three way hose.

Fastlane:
http://catalog.peachparts.com/item.wws?sku=W0133-1613948


The attached picture should make it clear.
Attached Thumbnails
Can I disconnect Windshield Heater ?-w126-windshield-heater-core.jpg  

Last edited by whunter; 06-07-2011 at 04:30 PM.
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  #11  
Old 12-26-2009, 03:49 AM
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I never knew my 126 had this feature. I do recall that my AUdi's and VW's had many more problems with the wipers freezing up, but I thought the Mercedes was just fortunate. Actually I think I noticed steam rising from the lower area of the windshield but assumed it was just a really effective defroster.

Wipers that hide in a trough are a pain in the...here in snow country. My Lexus, Camry and my Chrysler all suffer from Icy trough syndrome. Toyota's solution is a "Winter" switch which keeps the wipers up on the windshield when they are turned off.

I miss my 126. I wish I'd never sold it.
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  #12  
Old 12-26-2009, 10:50 AM
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Quote:
Originally Posted by Brandon_SLC View Post
Toyota's solution is a "Winter" switch which keeps the wipers up on the windshield when they are turned off.

I miss my 126. I wish I'd never sold it.
Sounds like a typical Toyota approach to the problem. A band-aid fix instead of a real fix. I drive every day in snow and bad weather, and my wipers work perfectly every time. The W126 is awesome!
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  #13  
Old 12-26-2009, 04:02 PM
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Quote:
Originally Posted by pawoSD View Post
Sounds like a typical Toyota approach to the problem. A band-aid fix instead of a real fix.
Yes. I was going to say that, but I talk too much as it is already.

Toyota probably does this so they don't have to replace wiper linkages, gears, etc. under warranty. Few owners even know about the feature, but it gives Toyota an easy out if your wipers break, because the feature is mentioned in the owners manual.
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  #14  
Old 12-26-2009, 04:45 PM
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Quote:
Originally Posted by whunter View Post
No.
His issue is that the wrong hose was ordered.
He got a straight hose = Two opening MB# 126 832 20 94.
The small steel windshield coolant return tube will be open.
The tube could be capped, however, it is easier to find/make a plug for the feed hose to the thermo-valve.

He needs MB# 126 832 30 94 ONLY FOR USE WITH WINDSHIELD HEATER = three way hose.

The attached picture should make it clear.
Thanks for the explaination and illustration, that makes it clear! I didn't have a 126 car in front of me and it's been about six or seven years since I had a problem with a pinhole leak in the heat exchanger on one of my SDLs. So I didn't recall the exact arraingment of the plumbing.
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  #15  
Old 12-27-2009, 12:31 AM
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When I first bought the SD back in 02, I replaced all the hoses under the
hood. one of them item # 71 in post #11, at that time was $85, while the
straight hose was $13.

we don`t get the cold and snow here on the west coast, so it isn`t that
big a deal to have.

I don`t know the price today, but still probably quite significant.

Charlie
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