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Thread: Rear window defrost/repair question

  1. #21
    Quote Originally Posted by tom1394racing View Post
    The best way to test the heating elements is to use a test light and a 12 V power source. Connect the positive lead of the power source to one of the tabs on the end of the heating element and the negative end to your test light. Very gently probe your heating element moving away from the positive connector along the heating element. As long as the test light lights, you’ve got continuity. I found with most of these old defrost windows, the heating elements are damaged, often very close to the power input source. I have never tried to repair one.
    I’ll give this a shot Tom, I’m just struggling to accept that all trace wires are open.

  2. #22
    Senior Member NorthernThrux's Avatar
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    This was my adventure with soldering them back on. https://www.early911sregistry.org/fo...is-cable/page3

    You should have an easier time. That said, its unlikely the horizontal wires will be functional after so many decades of oxidation.

    Ravi
    Early 911S Registry # 2395
    1973 Porsche 911S in ivory white 5sp MT
    2015 Porsche Macan S in agate grey 7sp PDK

  3. #23
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    when the 1st line opens all of the current goes through the balance of operating lines. as each line opens, more & more current is flowing through the rest.

  4. #24
    Ravi,
    Oh wow, identical to what i went through. Started at the switch and worked my way back to find these two wires. I have everything working accept the heat. Lol. Thanks for sharing. So what’s the end result, leave it alone? Buy a new back window? Any idea what they sell for? I might just button it up and revisit this “later”

  5. #25
    So it’s a domino effect to burn them all?

  6. #26
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    Quote Originally Posted by Rex1968s View Post
    Ravi,
    Oh wow, identical to what i went through. Started at the switch and worked my way back to find these two wires. I have everything working accept the heat. Lol. Thanks for sharing. So what’s the end result, leave it alone? Buy a new back window? Any idea what they sell for? I might just button it up and revisit this “later”
    On my '70 project, I left them alone. I do not expect to need the rear defrost function.
    Tom Butler
    1973 RSR Clone
    1970 911E
    914-6 GT Clone in Progress

  7. #27
    Member AKAMick's Avatar
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    They do sell repair window grid products that work well on other models of cars, https://www.ebay.com/itm/EASTUP-Rear...kAAOSwYwZcRZZk
    Last edited by AKAMick; 01-17-2021 at 12:09 PM.
    Current fleet, mostly rubbish automobiles and other assorted junk.

  8. #28
    Senior Member NorthernThrux's Avatar
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    Quote Originally Posted by Rex1968s View Post
    Ravi,
    Oh wow, identical to what i went through. Started at the switch and worked my way back to find these two wires. I have everything working accept the heat. Lol. Thanks for sharing. So what’s the end result, leave it alone? Buy a new back window? Any idea what they sell for? I might just button it up and revisit this “later”
    I was able to buy a NOS wiring harness here not too long ago, so my car is complete, even though the defroster is the one item that doesn't function after all those contortions. Sierra Madre does sell a properly tinted repro replacement window with defrost wires for my S. It's not crazy expensive, but my rear glass is original, so right now I'm in the "leave it as is" camp. Switch, relays everything work and I'll think about it some other time. So far have had no need for it and I drove well into the fall, but almost never in the rain. I invariably just leave the rear quarter windows open.
    Last edited by NorthernThrux; 01-18-2021 at 09:46 AM.
    Early 911S Registry # 2395
    1973 Porsche 911S in ivory white 5sp MT
    2015 Porsche Macan S in agate grey 7sp PDK

  9. #29
    So after doing a deep dive on the this-here’s why most of them done work.

    1) not laminated between panes
    2) oxidation, Brittle, chipped = open contacts

    Here’s a close up of the trace wires.

    Going with an after market might be the way to go, specially if they’re laminated between panes.


    P.S. just realized, removing the tint with soap and a razor wasn’t helping either. Lol
    Attached Images Attached Images   

  10. #30
    Member #226 R Gruppe Life Member #147
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    I fixed mine by buying a new rear window, don’t think I have ever used it, but it looks good.

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