From Alldatadiy:

The oil level is measured with a float (6) with ring magnet (7) and a contact
If the engine oil level is not sufficient, the contact (arrow) opens. the vehicle ground to base plate in the instrument cluster is interrupted and the indicator light (A1e12) comes on after a time delay of 60 seconds The time delay of about 60 seconds prevents the indicator light (A1e12) coming on if the car is accelerated or braked sharply or when cornering

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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe