On my W124's lower engine compartment?

124 520 27 24 Left
and
124 520 05 24 Right

Along with One (Each Side) ["Control Unit"]:
201 524 00 64

When the temperature inside the Engine Compartment reaches a certain level
the "Control Units" open the side Louvers increasing E.C. ventilation.
[Pre-Warm Up? 'Kinda Like the Three Stage Coolant Thermostat that allows
the engine to warm up to O.T. before opening?]

Shertex,

The "El Plastico" under Engine/Transmission "Anti-Noise" encapsulation provides
NO IMPACT PROTECTION from road debris.AND normal ATF will MELT the Rubberized inner covering.
However,there are Steel "Skid Type Plates" on some South African and European W124 s.
I've been trying for years to get some.

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'84 300SD sold
124.128