John:
Replacing the oil pressure sending unit is definitely a good start and the
most probable cause.
I have one other suggestion resulting from a similar problem experienced on
my TR-6. Near the oil pressure sending unit is a large headed bolt looking
gizmo which contains an over pressure relief. As I was breaking in my newly
overhauled engine, a few very small bits of metal shaving lodged between the
spring loaded relief pin and the seat precluding it from properly seating.
This resulted in slight internal seepage around the pin causing the light to
come on at low RPM when pressure was already reduced. At higher RPM the
light went out, although it was still seeping, presumably due to the higher
pressure resulting from higher engine RPM. It took about 15 minutes to
remove, disassemble, clean the assembly, and reinstall. A note of caution,
make sure you take the time to shine a flash light ("torch" for our British
friends!) into the block and inspect the seat for any arrant shavings and
dirt.
Make sure to thoroughly inspect the pressure sending unit hole before
reinstalling it as well.
Cheers!
Mark
73 Spit, 73 Stag, 73 GT6, 76 TR6 (all awaiting the arrival of spring in the
Rockies!)
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