next to the light switch there is a vertically-rotating control switch with a pictue of a head/fog lamp & arrows for up & down. what is this switch?

Headlight dipping control. You can point the headlights lower so they point down the road if the rear of the car is heavy. I don't understand the value of this in a car with leveling suspension.

Sixto
95 S420
87 300SDL

that's what i thought it was. found the vacuum lines today & they are plugged. i suppose they were not useful after the headlight ass'y. was converted to US spec. i can see nowhere to attach the vacuum lines. also, i don't think this car has self-levelling suspension.

Correct. US headlights don't have the actuators in them. The Euro's have a diaphragm inside the housing that will lower the beams slightly. Plugging the hose ends was the right thing to do.

NOW ... you need to find a set of Euro headlights.

__________________
Norm in NJ
Next oil change at 230,000miles

At European and the rest of the world markets, the rear self levelling suspension was only available standard on the W140s S 600, hence the headlight angle control was standard in all models.

The switch usually presents four settings: 0-1-2-3

0 - Standard (driver with or without a front passenger and with a full tank of gas).

1- Same as above plus a fully loaded rear seat.

2- Same as above plus a fully loaded trunk.

3- This position is recommended for heavy trailer towing.

The angle of aim is really dramatically varied, not just slightly.

By the way, the list above may differ from model line to model line. For example, my previous W123T (S123) 300TD Station Wagon presented the switch in this pattern: 1-0-1-2, where:

1 (above the cero) front passengers plus a fully loaded trunk, no rear seat passengers.

0 Standard

1 (below the cero) for fully loaded rear seat AND slightly loaded trunk.

2 Fully loaded car with or without a trailer.

I guess the self-levelling suspension on the T made the adjustment on the graphics. My W124 wagons all came with the regular 0-1-2-3 pattern.

__________________
A. Rosich
CL 500, 1998
S 500 L, 1998
E 320 T, 1995 [Sadly sold ]