How does a oil pressure sending unit work?

Answer 1

Answer 1To my knowledge there are three types of oil pressure sending unit.

The first is the oldest, and is nothing more than a port in the output side of the oil pump/engine oil gallery [passages] system, to which a tube is attached connecting the output to a mechanical guage on the instrument panel.

The next type is a screw-in device which has a diaphragm or a transducer which is attached to an electromechanical switch and by wire is connected to a light in the instrument panel. This is commonly refered to as an "Idiot Light." The sending unit is calabrated to turn the switch/electrical current/light on when the oil pressure is below a safe level for continued operation. As the oil pressure is generally directly proportional the engine RPM [revolutions per minute], the light tends to come on at very low idle speeds, and go out as RPM increases.

The third type is similar to the second type, except that it's electrical voltage output is directly proportional to the actual oil pressure, and when fed to an instrument panel electrical guage, will indicate the relative oil pressure [low, medium, high, and pressures in between.