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rear windshield defroster
https://www.slantsix.org/forum/viewtopic.php?t=29486
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Author:  stephaniebrite77 [ Thu Jun 12, 2008 11:39 pm ]
Post subject:  rear windshield defroster

While I was going through my wiring diagrams just to see what was there, I noticed wiring for a rear defroster. So now I'm curious. How were these mounted, at least for '65s? Were they just on the rear.. not sure what it's called.. the shelf thing between the back seat and the windshield where speakers are usually put.. facing the glass? I looked in my car, and I can see where there used to be *something* mounted in the center of the shelf-thing. ???? :shrug:
In any case, does anybody reproduce the rear defrosters, or are they a junkyard treasure? Did they even work well? A defroster for the back would come in real handy in the fall/winter/spring, and I've never been too big a fan of the way a grid defroster type thing would look on my car.

Author:  DusterIdiot [ Fri Jun 13, 2008 5:29 am ]
Post subject:  Lol...

Quote:
the shelf thing between the back seat and the windshield where speakers are usually put..
It's called a "package tray"... I think for your year the unit is mounted under the package tray in the trunk...(a blower and heat strip assembly)

-D.Idiot

Author:  Slanted Opinion [ Fri Jun 13, 2008 6:42 am ]
Post subject: 

Hi Stephanie,

I have seen the rear defrosters (original type) pop up on eBay once in a while.

-Mac

Author:  SlantSixDan [ Fri Jun 13, 2008 7:53 am ]
Post subject: 

Yup...if you remove the package tray upholstery trim panel, you will find three of what look like 6" x 9" speaker cutouts in a row (left, centre, right) and a narrow strip-shaped cutout aft of the central cutout, near the base of the backlight. The optional defogger was a blower type, without a heater. The motor, blower and housing were mounted to the central "speaker" cutout, finished with what looked like a speaker grille. The air was drawn in through this speaker grille, and there was a flex hose running from the housing to a plastic duct that fits in the narrow cutout (which itself is trimmed with a metal bezel plate topside). The air is blown out from this plastic duct and onto the inside surface of the backlight. Later units had 2-speed control, with the resistor mounted in the housing as is standard practice to keep the resistor cool, but I don't believe the resistor would produce enough heat to improve defogging significantly. These blower-type defoggers were certainly better than nothing, but they aren't anywhere near as good as the resistive-grid defoggers that were first offered on the A-body in '76. The '74 Valiant that lives across the street from me has a blower-type defogger; I'll try and snap some pics for you.

Backlight fog-up is a real damnuisance. It was one of the things I didn't like about my '65, particularly when driving in humid Oregon. Just not enough air circulation back there to keep the backlight clear, and Rain-X AntiFog just made a smeary mess. A blower-type defogger might've helped a little, but they really didn't work miraculously well. I think these days I'd probably take one of two different approaches to solving this problem:

1. The grid-type defoggers are built onto the backlight at the glassworks. The glass is etched, the conductive epoxy paint is applied, it's lightly baked to cure, and then the connector terminals are soldered or conductive-epoxied on. There've been aftermarket grid-type defoggers offered over the years, but these adhesive-backed grid lines generally don't hold up too well. The conductive epoxy grid paint is available at the consumer level, albeit in miniature little bottles. It'd probably be possible to find it in larger quantities with some sleuthing and persuasive calling. The critical part would be the etching, without which the epoxy wouldn't adhere to the glass. No problem there...you can get auto glass etchant from the companies that offer those VIN-etch security packages. Paint it on, wait awhile, rinse it off, and your glass is etched. If I were to do this, I'd either remove the backlight from the car or work with a spare. I'd carefully lay out the grid lines and bus bars using a mask/stencil made out of high-durability plastic tape, apply and then clean off the etchant (probably twice), apply a couple of coats of the grid epoxy, remove the mask/stencil, attach connector terminals with commonly-available connector terminal cement, and from there it'd be an easy matter of putting together a control circuit with a timer relay and momentary switch. Junkyard parts would be fine. Would this idea work in practice? I'm pretty sure it would, but it'd be easy to test it out by doing a trial run on a drinking glass, putting the glass in the freezer, removing it and letting it get nice and frosty, then applying power to see if the glass clears up along the lines.

2. Anti-fog film (see the second link in this post) applied to the inside of the backlight...and maybe the sideglass, too, while we're at it!

Author:  stephaniebrite77 [ Fri Jun 13, 2008 9:36 am ]
Post subject: 

Package tray.. so that's what it's called!! Nifty. I've always wanted to know what the proper term was. Thanks, DI.

Dan if you could get some pictures of the setup that would be rad, I really appreciate the offer. I've been really interested in knowing how it was all put together, and while the description goes a long way, seeing it would help heaps.

That anti-fog film looks really interesting. At $20-something/sq. foot it's a little pricey, but I think if I get some spare cash it may be worth giving it a try.

Thanks for all the info!!!

Author:  emsvitil [ Fri Jun 13, 2008 3:43 pm ]
Post subject: 

I'd think you could rig up a blower with a heater................

Author:  emsvitil [ Fri Jun 13, 2008 3:44 pm ]
Post subject: 

And I never understood the package tray...............

The way I drive, nothing would stay up there. :twisted:

Author:  SlantSixDan [ Fri Jun 13, 2008 3:47 pm ]
Post subject: 

"Package tray" is a really unfortunate name, because it leads people to do unwise things...like put stuff there. Anything you put there will become a dangerous missile aimed at you if you should stop short (like against another car).

Author:  Pierre [ Fri Jun 13, 2008 10:08 pm ]
Post subject: 

There was a mythbusters episode one time where they put a box of kleenex on the package tray and tested to see if it would fly with deadly force with abrupt stops. I forget the outcome...

I'm not so sure it would work well for car windows. Read page 9 of this pdf on their website.

Author:  SlantSixDan [ Sat Jun 14, 2008 7:41 am ]
Post subject: 

Quote:
There was a mythbusters episode one time where they put a box of kleenex on the package tray and tested to see if it would fly with deadly force with abrupt stops. I forget the outcome...
A box of kleenex won't kill you, even if dropped from atop a tall building. Higher-mass things will do damage and injury proportional to their mass. But the last thing you need when you're in the middle of an "incident", trying to control the car in an emergency, is a bunch of crap flying forward and hitting you, even if "all" it does is distract you.
Quote:
I'm not so sure it would work well for car windows. Read page 9 of this pdf on their website.
Interesting...their website mentions auto glass, but this what you point at suggests it might not work so well. I guess it depends on temperature differential, humidity, and other factors. I'm tempted to apply the film to one small piece of interior glass, or perhaps just apply a square of the film to a portion of the backlight, and see what happens.

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