Yes, it was standard beginning in '91, on US 124s.
No, the early switches do not have the contacts, BTDT.
Yes, it is useful in snow and fog, even heavy rain. In Europe you can be ticketed for using it when conditions don't warrant its use, I can't remember where I found this though.

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Gone to the dark side

- Jeff

When I gut the '94 I'll set the switch and the taillights aside for future use. As long as my '603 is healthy enough to be my daily I'll be tackling this over the summer.

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68 280SL - 70 280SL - 70 300SEL 3.5 - 72 350SL - 72 280SEL 4.5 - 72 220 - 72 220D - 73 450SL - 84 230GE - 87 200TD - 90 190E 2.0 - 03 G500

Nissan GTR - Nissan Skyline GTS25T - Toyota GTFour - Rover Mini - Toyota Land Cruiser HJ60 - Cadillac Eldorado - BMW E30 - BMW 135i

My '90 and '91 W126 coupes don't have the rear fog light, for some reason the US DOT did not allow them.

I'd like to have them, because they DO really work well in heavy fog

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1991 560 SEC AMG, 199k <---- 300 hp 10:1 ECE euro HV ...

1995 E 420, 170k "The Red Plum" (sold)

2015 BMW 535i xdrive awd Stage 1 DINAN, 6k, <----364 hp

1967 Mercury Cougar, 49k

2013 Jaguar XF, 20k <----340 hp Supercharged, All Wheel Drive (sold)

The W140's got functional rear fog light.

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Steve A
92 W140 OM603
97 VW Jetta TDI
90 Passat variant TDI 6 speed MT
94 Chevy K1500 6.5TD
05 E320 CDI
+ others