i currently have a 2 wire oil pressure switch in my tpi 400 in my 1974 caprice. this allows my motor to run but does not allow my original idiot light to work. heres the situation.

how my original 1 wire oil pressure switch circuit works is i got a wire that is hot when the key is in run pos. and goes through the indicator light to the pressure switch. if the pressure is too low (and i think too high) the oil pressure switch grounds out and the light kicks on

how my current tpi 2 wire(i think 89) oil pressure switch works is the oil pressure switch sits between the battery + and the fuel pump. in a situation where pressure is lost the switch will break the connection and the fuel pump will not be allowed to run thus protecting the motor. the guage or light is run from a seperate switch similar to the 1 wire switch mentioned above

MY QUESTION IS is there a 3 wire switch the can run the ground for the idiot light and the connection for the fuel pump all in one switch? i seen a part at autozone PN PS120 that may do the job but im not sure. and information on the subject would be appreciated. i think there was a gm switch used on 1.8 diesels that would work and others on silverados of some years that would work i just dont know exacly.

 

i would need a pigtail too so im looking for something they sell at auto zone

 

The oil pressure switch doesn't cut power to the fuel pump on low pressure.

 

The 3 wire oil pressure switch will run the fuel pump circuit in the case of ECM or fuel pump relay failure (just ike the 2 wire switch). Like mentioned, it does NOT cut power to the fuel pump, but rather the opposite - it sends power to the fuel pump as long as there is oil pressure. It is a back-up circuit for the fuel pump.

BUT - the 3 wire switch I believe is only good for guages and not idiot lights. I've never seen a 3 wire switch available for idiot lights.

 

that was to the best of my knowledge. do you know what cars do have 3 wire, guage senders?

 

Later models ... I know for sure 1990, 1991, and 1992 TBI cars did. I'm not sure any of the later models even had idiot lights - think they all had guages by 1990 (1990 started a slightly different guage design/layout along with the air bag).