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rear defroster

Interior and Electrical

  1. shadango

    shadango Well-Known Member

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    So the son is trying to hook up the defroster on the rear window of the 80 Volare today...

    The window was replaced at some point.....as evidenced by the broken glass in the car under seats etc when we had the carpet out, and the two tabs with broken glass stuck to them in the ashtray.

    Thing is, the defroster has me baffled.

    The son was gonna go buy a repair kit from the auto parts joint.....but I figured we should see if there is continuity across the grid before spending his hard earned moolah. And its when we try to check continuity that has us wondering...

    Should there be a metallic coating down each side? When he probes each side with an ohmeter, he gets continuity from side to side but ONLY when the probes are on what appears to be some coating. When the probes are on the clear part, no continuity.....but the "wires" seem to be made of the same clear stuff.

    We arent sure if all the wires are seeing continuity or if its just one or two and the rest would be dead.....

    If there IS supposed to be metallic coatings on the sides and all, then someone has scraped it off ...but why would someone do that? To a new window? That makes no sense....

    so in the picture below, the passenger side, you can see how thje whole side is clear EXCEPT a patch at the top..this is where we can get continuity. Anywhere else, no.

    IMG_20170822_121439.jpg
     
  2. shadango

    shadango Well-Known Member

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    And here is the driver side.....most of this side has this coating.....

    What is baffling is the "wires" look the same as the clear part on the passenger side.

    driver side.jpg
     
  3. BudW

    BudW Moderator Staff Member

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    Before I get started, I want to say that I have very limited experience on the back glass grid repair and diagnosis of the actual glass grid.

    Also, I want to say the use of rear “defogger” and “defroster” terms is rather confusing and would prefer people to use the term “heated back glass” or “black glass blower” system, instead.


    Now the back glass switches – I have replaced many of, over the years.
    Matter of fact, I need to replace the heated back glass switch/relay on both my ’77 wagon and on my ’86 5th Ave (one of these days . . .).


    I attached a copy of the heated back glass diagnosis and repair pages from my ’77 FSM as well as from my ’86 FSM (on a different post).
    BudW
     

    Attached Files:

  4. BudW

    BudW Moderator Staff Member

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    From my '86 FSM
     

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  5. shadango

    shadango Well-Known Member

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    Thanks Bud

    If anyone has pictures of their WORKING heated back glass system that are similar to the ones above so we could compare, that would be very helpful.

    After looking around on the web though I think what happened is the previous owner had installed tint on the back window...and before we bought it, the tint was removed --- removing most of the metallic parts of the side bars and the grid lines at the same time.....

    I think the only real fix would be to replace the glass with a new grid on it already or scrape off the old lines on the current glass and replace the grid itself...found a lot of info at this site where they sell replacement grids....

    Frequently Asked Defroster Questions
     
    Last edited: Sep 13, 2017
  6. BudW

    BudW Moderator Staff Member

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    Pictures I just took of my ’77 wagon.
    Note: I need to wash the car so – don’t pay any attention to the, um, dirt.

    20170913_161610.jpg

    20170913_161647.jpg

    20170913_161654.jpg

    20170913_161708.jpg

    This defroster system does not currently work. I’ve not spent any time looking into why for I don’t need/use it that often. I’m going to guess it is a bad switch (my guess is a 95% chance of switch failure). I will test it before replacing it, though. The light operates for about the normal time frame, then auto kicks off – but no actual defrosting occurs.

    - - - -
    If you have a grid wire that has a break in it – then that line will not heat up (until you get that grid line/wire fixed first).

    Ice scrapers used inside of the car, is murder on those grid wires!
    Tint usage and tint removal is ranked only slightly lower (than murder).
    BudW