On Tuesday, 21 May 2019 10:48:29 UTC+1, Dave Plowman (News) wrote:
Old car has a low oil level sensor, which has never really worked
properly. And spares for it NLA.

It has a probe in the sump about 2" long, which merely screws in. Doesn't
tell you the oil level as such - just warns if it gets too low.

I've looked for a modern aftermarket set (probe plus electronics) but
can't find anything.

I've also no idea on the principle of how it works.

It is connected to the inlet manifold with apipe
When the hole is immersed in oil, a vacuum is created.
When it it exposed, there is normal air pressure.

So all there is, is a switch measuring the vacuum or lack thereof.