Automotive Mileposts  

Quick Defrost
Windshield and Rear Window

A transparent, gold-bearing metallic film made it happen

Quick Defrost graphicUsing 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.

1975 Thunderbird with Quick Defrost gold film rear glassKnown 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.


1974 Mark IV | 1974 Thunderbird | 1975 Mark IV | 1975 Thunderbird | 1976 Mark IV | 1976 Thunderbird

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