im guessing the sensor is on the sump somewhere
On these the oil light will only come on due to low oil pressure...
Its not an oil level warning, as there is no oil level sender until you get to much newer vehicles.
Althought obviusly having a low oil level may give you low oil pressure!
There are usually two oil pressure switches, at two different pressures, there exact location depends on engine, but are usually on or near the cylinder head.
If you have checked the level and it seems okay, then its going to be somthing else....
The things that come to mind are:
Dodgy oil pressure switch,
corroded plug or damaged wiring to pressure switch,
blocked sump pickup,
oil pump problems,
sticky oil pump pressure releif valve,
blocked oil filter.
