The dreaded w126 rear windshield milky white/ delamination syndrome is manifesting itself on the '85SD passenger side rear corner. Only the upper 25% of the glass heats up - the wires show corrosion where the discoloration is seen.

Located a good seeming replacement at the pick and pull. How to test it before pulling?
Also, will any year fit?

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'83 SD, 2x '85 SD
You are entitled to your own opinions, you are not entitled to your own facts.

You can use your volt/ohm meter to see if there is continuity and that could tell you if it has a open circuit/dead (a test light that has a battery would also work) but that won't tell you if all of the grids are function.

I have not been to a junkyard out here for a long time but it used to be you could purchase a warranty on the part you take of. However, the warranty only covered you getting another used part.

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84 300D, 82 Volvo 244Gl Diesel

Unscrew the leads, one on each side edge of the glass and test the resistance between them.

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84 300SD
85 380SE
83 528e
95 318ic

Unfortunately all that will tell you is that you have at least one good wire.

The only real way to check is power up and do an IR scan. Unfortunately not everyone has one of those in their back pocket...maybe soon the price on those will come down to where they are commonly affordable.

Only other thing I can think of is that you will get a magnetic field around each conductor, and only the lines with continuity will pass current and thus generate a field about that line. May have to do an experiment with a compass and see if it is capable of detecting the field in each grid line and resolve to tell if a line is carrying or not. Or maybe a Hall effect sensor.

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The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

That is what I was trying to say.

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84 300D, 82 Volvo 244Gl Diesel

How about icing up the glass with dry ice and seeing if it clears all up and down the window in that way typical of an operating defroster?

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'83 SD, 2x '85 SD
You are entitled to your own opinions, you are not entitled to your own facts.

Hmm... the pocket compass idea has some merit. I'm betting even a small battery, connected to the terminals, might be sufficient to cause a fluctuation of the needle when you scan it from top to bottom. It's worth a shot!

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Sam

84 300SD 350K+ miles ( Blue Belle )

Measure the current consumption!

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Yes with an ammeter but you would need a known good rear window to get a reading from and then you would need to take a Car batter with you to the Junk Yard so you could take a reading there.\
The tough word there is Junk Yard.

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84 300D, 82 Volvo 244Gl Diesel

Why "tough" ? you're in Long beach where there are lots of junk yards and one of the larger LKQ Pick-A-Part ones with usually lots of Mercedes W123's & W126's....

They're the cheapest in town too ! I just bought a 6 disc CD changer for $18 + tax .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

CD?
Every thing I do on my Car in my drive way is easier then in Junkyard therefore what is done at a junkyard is tougher.

In fact for me just getting in and out of the rear seat of a Car (to hook up wires to test a rear window) propped on top of a bunch of welded together wheel rims would be more difficult.

They of course unless you have like a 12 volt lawn mower, motorcycle or small battery you have to transport the full sized car battery into the Junk Yard and I don't know if they would even allow that.

I bet I have not been to junk yard since before 2011. In 2011 I broke the ball off of my Hip Bone. Since that time my interest in dragging myself around a junk yard has been severely curtailed.

Also in the 2 junk years I used to frequent W123's were in the minority compared to SDs

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84 300D, 82 Volvo 244Gl Diesel

I can dig your sentiment .

It's a Direct Current powered CD player, does that cut me any slack ? .

I didn't think so, blame it on my fat fingers, they match my head .

I grew up working on rusty old farm junk in the mud or on ice in a drafty barn, having a paved junkyard to work in in California was an up grade .

Hobbling 'round the yard on my cane isn't much fun either but I do what I gotta do .

Junkyarding was fun as a young man , now it's my regular exercise .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

That is plausible, except that you won't be able to detect that you have a few open wires that way.

Same reason you can't reliably flush out a parallel flow condenser or a radiator.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

If you measure one with no open wires, then measure another and get the same amperage, it also has no open wires.

__________________
85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Get a can of cold spray. Put a battery or booster cables on. Turn the rear defroster on. Spray a vertical pattern down through all the strips after letting them warm for a minute. You should see if all are heating or not.


Unless breaks are always visable to the eye you have to power it up. A hand held spot temperature reader would also do it. Read the strips from the inside though.