Either the oil pump on the vehicle has failed which is highly unlikely. More than likely the oil pressure sending unit is defective. Replace the sending unit and if the problem is still there seek professional help. Do not drive this vehicle until you solve the problem.
Oil level and oil pressure are different. You don't need to have full oil to get normal pressure.
That would not account for loss.
oil pump/ main bearings/ severe oil leaks/
The pressure will be high until the oil reaches full operating temperature.
Yes, it can. It measures the engine oil pressure and if it fails, the pressure can come through it losing oil.
If the oil level is fine then either the oil pressure sending unit is defective or the oil pump has failed.
Low oil pressure. Such as a bad oil pump.
there is no oil pressure in my 1997 ford taurus, but the oil is full?
If your oil level is full and you have low oil pressure it can be nothing more than a defective oil pressure sending unit or defective gauge. But, it can also be a weak oil pump. I would replace the filter first thing and add enough oil to reach the full mark and see if the condition goes away. If not, then replace the oil pressure sending unit.
Yes, oil can leak through the switch.
Assuming you mean oil pressure, check all the fluid levels NOW. You may be low on oil.
Pull over and kill the motor immediately when you lose oil pressure, failure to do so will destroy the engine.