My rear window demister switch lights up when pressed to indicate that it is working however it appears to do nothing. When looking at the rear window I cannot see the typical heated lines that are usually on the inside of the glass. Am I missing something or is there an alternative method of demisting that I can't see.

Maybe you're not looking closely enough. The wires are very thin. Also, if you're accustomed to the inch-apart spacing on most American or Japanese cars, the wires in the W126 rear window are only about 5 mm apart. Yours may be all working (I have a dead strip an inch or two wide) so you probably won't see any kind of lines. Are you getting any defrosting action? My guess is that it's working so fast you won't see any of the defroster lines.

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Bob Roe
Lehigh Valley PA USA
1973 Olds 88, 1972 MB 280SE, 1978 Datsun 280Z, 1971 Ford T-Bird, 1972 Olds 88, 1983 Nissan Sentra, 1985 Sentra, 1973 230.6, 1990 Acura Integra, 1991 Volvo 940GLE wagon, 1983 300SD, 1984 300SD, 1995 Subaru Legacy L wagon, 2002 Mountaineer, 1991 300TE wagon, 2008 Murano, 2007 R320CDI 4Matic 52K, some Hyundai, 2008 BMW 535xi wagon, all gone... currently
2007 Honda Odyssey Touring, 2014 E350 4matic

This morning my window was moderately frosted and I had the demister on for about 15 minutes with no apparent result. I will look closer tonight as I am used to the inch wide strips.

Well after closely inspecting the window I cannot see the strips and the window is definitely not getting demisted. Is this a typical demister in that it is stuck on the inside of the rear window? If so is this something that I can purchase and install?

Cheers
Matt.

The lines are extremely thin and are probably sinus-shaped and may be running vertical instead of horizontal...
It is not something that you can purchase and install, it is something that is mounted between the glass layers.

You might want to remove the C style panels to check whether there is power at the connection points.

greetingz,

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1990 300SL-24
1993 C250D with a minor 600+k kilometer
www.MBenzNL.com(the Netherlands)

Thanks for the replies, is there two power connection points ie one each side or only one? Would the light be lit even if there was a dead circuit? Is there a fuse just for this function?

Cheers
Matt.