Electrical function of coolant level indicator - RA20001194400X(20-4400)

WARNING: This page does not describe the selected car, but rather 42 other vehicles, including the 1999 Mercedes-Benz S600, 1999 Mercedes-Benz S500, 1999 Mercedes-Benz S420, 1999 Mercedes-Benz S320, and 1999 Mercedes-Benz CL600. However, it is still accessible from the selected car via links, so may be relevant.

Model 124

Fig 1: Electrical Function Of Coolant Level Indicator (Model 124)
Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

General

The coolant level indicator monitors the coolant level in the expansion reservoir (1) when the engine is running.

When the ignition is switched on, the indicator lamp (A1e11) lights up weakly (check function) and goes out as soon as the engine is started provided the coolant is at correct level.

The coolant level sensor (S41) has two retaining lugs of different width and can be installed only in one position. It is sealed by means of an O-ring (52) and fixed in position by a circlip (55).

Function

If the coolant is at the correct level a permanent magnet (2) in the float (51) and a permanent magnet (3) in the sensor (S41) hold a contact (arrow) open.

If the coolant level is too low the float (51) moves down and the permanent magnet (3) closes the contact (arrow) in the coolant level sensor (S41). A permanent input signal (vehicle ground) exists at the base plate (a) of the instrument panel unit (A1) and the indicator lamp (A1e11) lights up brightly.
Models 129, 140

Fig 2: Electrical Function Of Coolant Level Indicator (Model 129, 140)
Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

General

The coolant level sensor (S41) is not directly enveloped in coolant and can be removed and installed without draining the coolant in the expansion reservoir (1).

Function

If the coolant level is too low the ring magnet (54) in the float (1) closes the contact (arrow) in the coolant level sensor (S41).

The permanent input signal (vehicle ground) exists at the base plate (a) of the instrument panel unit (A1) and the indicator lamp (A1e11) lights up brightly.