In my 86 300E...
The oil light has started coming on as soon as the car has started (as opposed to the usual warm-up period it seems to need), and comes on regardless of oil level. Is this just a sensor or wiring problem? Got an easy fix for someone with time to waste on the car, a service CD and a hatred of idiot lights?
Thanks all,
-Nick

Your oil level sensor is the problem,the sensor is locate at left side of oil pan with one black wire connected,here is how to test your sensor just disconnect the black wire the light should off.
hope this help.

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MB STARS Master Guild Technician,12 years MB tech
6 years independent shop owner