Oil Level Sensor: Description and Operation

GF18.40-P-4114AMG Component Description Of The Oil Level Check Switch
ENGINE 156.980 in MODEL 164, 251 up to Model Year 8
ENGINE 156.982 in MODEL 209
ENGINE 156.983 in MODEL 211, 219
ENGINE 156.984 in MODEL 216, 221 up to Model Year 8





Location for an engine with front sump (Engine 156.980 in model 164, 251)
S43 Oil level check switch

The oil level check switch is located at the right front in the oil pan top section.
The connector for the oil level check switch is located at the right front on the oil pan top section.





Location for engine with rear sump (engine 156.982/83/84 in model 209, 211, 216, 219, 221)

1 Oil pan top section
S43 Oil level check switch

The oil level check switch is located at the rear front in the oil pan top section.
The connector for the oil level check switch is located at the rear front below the oil pan top section.

Task
The oil level check switch recognizes the minimum oil level in the engine oil pan and reports going below the minimum oil level to the ME-SFI [ME] control unit (N3/10).





Body (shown with sufficient engine oil level)

30 Float
31 Ring magnet
32 Dry-reed contact
34 Ground contact
39 Base plate
41 Switch housing
S43 Oil level check switch

Function
The engine oil from the engine oil pan reaches the oil level switch via 2 bore holes in the switch housing. The float is moved according to the oil level. The dry-reed contact is closed for an adequate engine oil level by the magnetic field from ring magnets.

If the engine oil level becomes too low the dry-reed contact opens and the connection to the ground contact is interrupted. This recognized by the ME-SFI [ME] control unit and a suitable warning signal is sent via the CAN data bus to the instrument cluster (A1).

Short-term fluctuations in level are compensated for by to the size of the oil volume and the 2 bores in the switch housing (e.g. during braking or for cornering) which avoids unnecessary warning signals.