If your Milano has reached midlife, there's a good chance that the sensor that detects a low engine oil level has started to malfunction. There are two ways that a failure can show up: Either the warning light comes on when it shouldn't or the warning light doesn't come on when it should. For me, the second failure mode doesn't not present a problem since I check regularly using the dipstick anyway. The very fact that these things fail so often makes that a good idea anyway. What does bother me though is when there's an annoying flashing red light on the dash...especially when you are giving guests a ride and they ask if something is wrong with your Alfa!
So when my warning light started flashing permanently, I had to do something about it. I first verified that it was actually the sensor that was bad. Measuring the resistance across the two terminals showed an open connection. It should be 13 ohms. After taking the sensor out and convincing myself that it couldn't be fixed, I was faced with a decision: do I buy a new one for nearly $100 just for the sake of having it work properly, or do I bypass it knowing that I would never trust the sensor anyway. Having limited resources and knowing that that the $100 could go towards new Konis instead, I chose the later.
In order to understand how to bypass the sensor, I first had to understand how it operated. The shop manual came in handy here. There is a decent description of the Alfa Romeo Control (ARC) computer and all it's associated sensors. The Oil Level sensor is composed of a heated coil (13 ohms) and a bimetalic switch connected in series. When the ignition is first turned on, voltage is applied to the sensor. If there is no oil in contact with the bimetalic switch, the coil will heat it and open the circuit. If there is oil in contact with the switch, the oil will absorb the heat generated by the coil and the switch will remain closed. After a few seconds, the ARC checks to see if the circuit is open or closed. If open, it lights the warning light and keeps it lit until the ignition is turned off.
With this information, I knew that simply disconnecting the sensor would not work. It would simply act like an open circuit and the light would come on. Shorting the circuit also would not be a good idea since this is connected directly to the computer which may object to a zero resistance by frying itself. The obvious choice was to place a resistance in the path equivalant to the resistance of the coil - 13 ohms. This would act just like a sensor whose switch did not open. Well, I didn't have a 13 ohm resistor, so I tried a 100 ohm one...and it did the job.
I made the bypass more appealing by covering the resistor in shrink wrap
tubing and soldering a male terminal on each end. This way, if I ever
decide that I just need that sensor working, I can just unplug the bypass and
plug in a new sensor.