Rear Defogger Glass Discovered!!

[bossanov]

With total help from Senior Member Walter Klatt, I have been in the process of restoring a 71 Pagoda that has thee rear defogger option.  However, not being able to see any heat filaments in the glass, I decided that this was not the original glass and have been searching for a heated replacement glass with no luck.  I read recently on this forum that the filaments are almost invisible, so this morning I rolled the HT outside, cleaned off the dust from the glass, took off my glasses and viola!, there beforem my eyes appeared the elusive zigzag filaments that we were unable to see previously.  I am so happy!!

Bossanov
1971 280SL Horizon Blue (under restoration)

[CraigD]

Bossanov,

Is the 3-prong pigtail present on the top, too?  It's connected to the underside of the hardtop beneath the driver's side 1/4 window, and plugs into a female receptacle wire on the car.

[bossanov]

Bossanov,

Is the 3-prong pigtail present on the top, too?  It's connected to the underside of the hardtop beneath the driver's side 1/4 window, and plugs into a female receptacle wire on the car.

Yes, the pigtail and console switch are both present. Also, the datacard indicated this option was included.  It was just that the filaments are so tiny that we presumed the glass had been changed.

[RickM]

Interesting. I'm guessing I haven't looked close enough at my rear window.

I saw the pigtail but didn't see any filaments when taking a quick glance. I assumed I had an unheated rear glass.

I do have code 249 in the first wenig gewunscht field of my data card. I believe that translates to "Rear Window Electrically Heated and Heat Absorbing Glass"

Does this code pretty much confirm it left the factory with this option?

[dtuttle123]

I love it when you discover that you really didn't have a problem!  It will be the least expensive 'fix' on your 280SL!!

[bossanov]

Interesting. I'm guessing I haven't looked close enough at my rear window.

I saw the pigtail but didn't see any filaments when taking a quick glance. I assumed I had an unheated rear glass.

I do have code 249 in the first wenig gewunscht field of my data card. I believe that translates to "Rear Window Electrically Heated and Heat Absorbing Glass"

Does this code pretty much confirm it left the factory with this option?

Right, that is the factry code. Make sure you look very closely at the glass from an angle.  The filaments are smaller than a strand of hair and run horizontally in a zizzag pattern approx 1 cm apart.   Unlike the ones in newer cars, they are a lot of them.

Please let us know what you find.

Regards,
Re

[bossanov]

I love it when you discover that you really didn't have a problem!  It will be the least expensive 'fix' on your 280SL!!

This is so true.  And to add to it, we really cannot replace this glass because they are no longer available per MB Classic Center.

[RickM]

Quote: Right, that is the factry code. Make sure you look very closely at the glass from an angle.  The filaments are smaller than a strand of hair and run horizontally in a zizzag pattern approx 1 cm apart.   Unlike the ones in newer cars, they are a lot of them.
Please let us know what you find.
Regards,

I will look much closer and attempt to take a pic....

[RickM]

Wouldn't you know, I have those nearly invisible filaments. It took a couple trys before I could see them.

As mentioned I'll do my best to photograph and post.

[RickM]

Still working on the pic of the embedded filaments....it's tough to focus within the layers of laminated glass on such a fine scale.

In any case, the "label" at the bottom left of the rear window likely says it all. I'd imagine the wavey line and/or the D-148 denote a heated window. Can we compare to a standard glass?

Bossanov: Do you have the same info on your label and is your car a US model?




Update:

Therglas holds patents specific to "emplacing" fine filaments into laminated glass for the purpose of heating while retaining transparency.


Therglas gmbh fur flachenheizung (for flat heating)

"4284452 - Method of embedding thin wires in laminated glass
The invention relates to a method wherein thin wires are three-dimensionally embedded in a uniformly finely undulating manner in the intermediate film of laminated glass by filaments of the same base material as the intermediate film with wire wound around them in stretched helical coil configuration being pressed into the film and made to disappear during the pressing procedure to form the laminate. Manufacture is simplified, economical and efficient. Also, better visibility conditions are obtained..."

[bossanov]

RickM,

I was not able to get a good picture of my glass label, but comparing it to yours it is quite similar.  Here are the differences:

Kinonglas-Kristall / S - HI
M31 / AS2 Plate
/\/\/\/ D - 97

Hopes this helps.

[RickM]

Thanks for the feedback. I'm guessing it says Therglas as well?

Just curious......

[bossanov]

Thanks for the feedback. I'm guessing it says Therglas as well?

Just curious......

RickM,

Yes, all the other markings are identical to yours.