1974-1976 Mark IV Super Defrost Option

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1974-1976 Mark IV Super Defrost Option

Post by 78_towncar_460 »

I know there was an option available for the Mark IV that allowed a fast defrost via a layer of gold film imbedded into the windshield. I read that there was a second alternator installed on these cars. Just wanted to know more about that specific option. I saw a 'gold' windshield for sale on ebay a while ago. Did these cars really have two alternators? I seem to recall a user "Joe Nemec" having a pristine 76 Mark IV with this option. I looked in the photo gallery at engine pictures of that Mark IV but could not really see a second althernator.

Does anyone have one of these systems in their Mark IV or Thunderbird?
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Re: 1974-1976 Mark IV Super Defrost Option

Post by Dan Szwarc »

I've seen pics of the cars with two alternators, but never in real life.

They exist, but not many of them.
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Re: 1974-1976 Mark IV Super Defrost Option

Post by AlT63bird »

Same setup was used on both Mark IV and the T-birds. I have documented a couple of 'Birds with the dual alternators, but that was pre-digital days when I lived in Wichita for a couple of years. Heaven help the person who needs to replace one of those windshields.
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Re: 1974-1976 Mark IV Super Defrost Option

Post by Linmk56 »

Yes, Marks so equipped did have two alternators. The windshield was based on aircraft technology. In my days with Lincoln/Mercury dealerships I only saw one car so equipped. It was a car we bought at a Ford auction as a used car. That car had two alternators. Here is a write-up about the feature:

Using the same space age technology as the Boeing 747 electrically heated windshield, Ford's Quick Defrost Windshield/Rear Window option was introduced in 1974 on two of its top of the line prestige cars, the Ford Thunderbird and Continental Mark IV. Laboratory tests at the time showed that Quick Defrost cleared frost and thin ice from windshields five times faster than typical forced warm air defrosters, and three times faster than conventional electric grid-type rear window defrosters.

A transparent, thinly coated gold-bearing metallic film is sandwiched between layers of polyvinyl butyral and glass. When electrical current is applied to this film, it warms quickly and evenly to rapidly clear the glass of frost or ice. A second alternator is provided on cars equipped with this option, and two defrost power levels were provided: high for initial fast clearing, and low to keep the glass clear. After three to four minutes of operation, the glass areas are mostly cleared.

To operate, the engine must first be started. The control switch is moved to the right to activate the system. The system operates on high for ten minutes, then switches automatically to low power. An additional ten minutes of high power can be had by manually turning the control switch off, and then turning it back on again. Once on low power, the system will remain on until turned off manually, or when the ignition is turned off.

One characteristic of this glass is its distinctive gold tint, clearly visible from outside the car, but barely perceptible from within. In addition to fast defrosting, this film layer laminated within the layers of glass rejects non-visible solar heat, which improves air conditioning performance during the warmer months.

Known in the glass industry as the DW825 windshield, this option was short lived due in part to its cost, which was $306.70 on the Mark IV in 1974, and peaked at $360 on that same model in 1976. Service replacement glass was discontinued within a short period of time, which forced many cars with chipped or cracked glass to have conventional glass installed in place of the Quick Defrost glass. The conventional windshield is listed as DW792.

Some collectors insist that Quick Defrost glass that sits dormant for long periods of time without being activated can fog over, permanently ruining the glass. While this has not been proven to be the case to Automotive Mileposts, we firmly believe old cars should be driven as regularly as possible, and anyone who happens to have a Thunderbird or Continental Mark IV with the Quick Defrost option would be well advised to activate the system on a regular basis, just to ensure all is well and to eliminate the possibility of fogging from inactivity, in the very likely case that there are indeed a few folks out there who know more than we do about this system.
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Re: 1974-1976 Mark IV Super Defrost Option

Post by RyPow »

This was also known as the "Sierracin" window option, was it not?

IIRC, some of the '80s Panther-body cars (perhaps just the TC but maybe the Grand Marquis/Crown Vic as well) had this option as well.
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Re: 1974-1976 Mark IV Super Defrost Option

Post by Spot »

Theres one guy from California? which has a Mark IV with this option.
Unfortunatly I forgot his name.... but you can also find him on cardomain !
He uploaded a lot and very nice pics of his beatiful car.
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Re: 1974-1976 Mark IV Super Defrost Option

Post by thegermanfan »

The Sierracin Corporation (Sylmar, CA) apparently owned the patents for this glass. Hence that name. The power consumption of the quick defrost system was quite substantial and interestingly unregulated. With higher rpm the output voltage also increased.
Today this is marketed as a TERRIFIC NEW development. The 2011 VW Passat boasts such a quick defrost windshield.
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Re: 1974-1976 Mark IV Super Defrost Option

Post by bob sandercock »

I saw a 75 MKVI at an auto wreckers a few years ago and was tempted to try to get the windshield etc. out but didn't have the time.
Looking back I wish I had
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Re: 1974-1976 Mark IV Super Defrost Option

Post by MMM »

I believe it was called Quick Defrost on the Mark IV's. My father once had a late production Ginger Moondust '73 with it. He loved it.

In '89, the option was available again on Continentals and called Instaclear. Not sure if changes were made in the tech behind it vs. the Marks.
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Re: 1974-1976 Mark IV Super Defrost Option

Post by action »

Insta clear was available in the '80's with the Ford line for T-Bird and Taurus in the front windshield. I have seen a Taurus so equipped when I worked for Ford Parts and Service Division. It was an expensive option that was not popular.

That option mentioned in the first post can be seen here.
http://automotivemileposts.com/mark4197 ... pment.html

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