I don't know about 1999 model, but my 2000 ML430 had integrated fog lights.
They are in the same housing as the normal headlights. I asked my dealer to
activate them when I bought it new. It appears(don't know if this is true),
but some states in US consider them illegal because they are too high.
Except for those equipped with HID lights, all ML's from 1998-2001 have fog
lamps integrated into the headlamp assembly as well as a connector for
external fog lamps. Both are controlled by the same switch on the dash to
the left of the radio. The connector for the external lamps can usually be
found capped off, hanging between the radiator and the port-side headlamp
(that is on your right if you are standing in front of the open hood). It
may have a white tag on it indicating the maximum wattage. The integrated
headlamps are additional sockets (for an H3 bulb) located on the
inboard-most section of the headlamp assemblies.
To use either set of fog lamps, you will have to have the AAM (All-Activity
Module: the computer system that controls all the ML's non-engine functions)
programmed to enable the switch and, if you want, the indicator light on the
instrument panel. Because many states have laws that limit the height of
fog lamps, and the ML's integrated fog lamps exceed this limit, the option
is usually not enabled by default. Some 2000 and 2001 models were shipped
with it enabled, but most 1998 and 1999 models were not. To test it,
install H3 bulbs in the integrated sockets, start the engine (it MUST be
running), turn on the low-beam headlights, and press the top half of the fog
lamp switch. If they do not illuminate, then your switch will have to be
activated by the dealer. Because of the laws, many dealers will not
activate the switch unless it is being used to power external,
legally-oriented fog lamps. In this case, they may charge a fee. Also, the
instrument panel indicator is a separate setting. Some people do not
activated it because it is annoyingly bright; the same as the high-beam
One note of caution. If you do use the fog lights, either integrated or
external, make sure you check the leads in the headlamp assembly used to
power the integrated lamps. Often, the factory will "trap" the leads under
the metal clip for the bulb. This can cause the insulation on the wire to
be cut, and if any bare wire contacts the metal bulb housing, you will blow
the fuse. Mine was this way so I ended up having to wrap the leads with
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