idiot light problem

[Flanders <flanders@earthling.net>]

Greetings,

My wife's 1990 200TQW is acting up. Can anybody out there help? The low oil
idiot light is coming on at random. It happens more often after the car has
been sitting in the sun or after a series of short trips. The oil pressure
and oil temp gauges are both reading fine, but the dash board warning goes
off for no apparent reason. We have had two mechanics trouble shoot it, one
dealer and one independent, but so far no luck. The sensor and both sending
units have been replaced. Now what do I do?