Engine Two wire oil pressure wiring

[SwampRatt]

I have a 79 CJ7, 304.
My oil pressure sender has 2 wires coming off it.
One should be the oil pressure gage and the other is red but is terminated
In the harness.
I have heard about a low oil pressure switch that prevents the engine from
Starting or running if the oil pressure is low.
If this terminal is that mythical switch how does it work?

 

[CJ]

No such stock sender for a 1979 CJ V8. It has one wire oil pressure sender. You can wire in a two wire for a light / gauge.

 

[TSB8C]

I believe the two wire sender is actually a switch for an idiot light. A "sender" to drive an analog gauge only has one wire (and the case is grounded through the mounting). Since that same engine is used in many vehicles, some would not have a gauge (like a CJ does) and would use the light instead. For the CJ with a gauge, you need the one wire sending unit and not a two wire switch.

Now if you wanted a low oil pressure switch to prevent the engine from running, you could wire a relay into the ignition circuit and drive the relay from such a switch. The relay would need to be a 5-wire type with a N/O and N/C connection. Use the normally closed connection to complete the ignition circuit when the relay is not energized. Then a low oil pressure switch would energize the relay (just like turning on an idiot light in the dash) and the energized relay would break the ignition circuit, killing or preventing the engine from running.

 

[Armyvet25]

or...get an actual mechanical oil sending unit and gauge for a more accurate reading

 

[SwampRatt]

I believe the two wire sender is actually a switch for an idiot light. A "sender" to drive an analog gauge only has one wire (and the case is grounded through the mounting). Since that same engine is used in many vehicles, some would not have a gauge (like a CJ does) and would use the light instead. For the CJ with a gauge, you need the one wire sending unit and not a two wire switch.

Now if you wanted a low oil pressure switch to prevent the engine from running, you could wire a relay into the ignition circuit and drive the relay from such a switch. The relay would need to be a 5-wire type with a N/O and N/C connection. Use the normally closed connection to complete the ignition circuit when the relay is not energized. Then a low oil pressure switch would energize the relay (just like turning on an idiot light in the dash) and the energized relay would break the ignition circuit, killing or preventing the engine from running.

Yep, my bad. Crawling around under jeep looking up all I saw was the pressure switch. I missed the pressure sending unit up top of the oil filter.
Thanks for the replies folks,