Quote:
Originally Posted by HPsauce
It was a pretty rare option.
Back then the patents/licences for it were almost all held by Ford which is why they had it relatively widely available, even on my 1998 Focus (one of the first out of the factory).
I presume Audi decided to pay the fees to Ford for their premium model range. And I'd guess Ford would be happy to take the money as they had no competing model.
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The Ford system has visible wires inside the glass, which can be a tad distracting in night-time headlamp glare. It was used in aircraft during WW2 so perhaps any patents have expired. I actually have this on a VW.
The Audi system energises a tin dioxide layer that is deposited on one of the inner surfaces of the laminated glass. When a current is applied across the glass resistance in the metallic layer causes it to heat up, and in turn warms the glass.
IMO it's the best system out there. Very fast and invisible.
BTW your engine needs to be on for the heated front screen to operate.