Oil pressure send- 6V92?

[chuckdrum]

To my always helpful busnuts at BCM-

I've been having issues with my oil pressure gauge for some time; as in, it registers nothing.  The gauge itself and the dashboard wiring *seem* to be fine.  I suspect the problem is with the send.  And my problem is that I don't know what I'm looking for!

Attached is a photo of the driver's side of my 6V92.  There are three switches/sends attached to a hexagonal tube.  The wiring to the middle switch appeared frayed so I replaced the end.  After doing that, I got a brief reaction from the dashboard gauge when I started it up.  Then the gauge went back to zero.  So I'm thinking I'm on the right track here.  Would just like to know what I'm looking at here, what I need to replace, and the correct terminology to use when seeking the part.

Thanks!!
Chuck

[Geoff]

Oil sending units work off the resistance of the sender.  If you jump the terminal at the sender on the engine to a ground, you should read maximum pressure at the gauge. If not, the problem is not your sender, it is either the wiring or the gauge itself.

--Geoff

[Oonrahnjay]

Oil sending units work off the resistance of the sender.  If you jump the terminal at the sender on the engine to a ground, you should read maximum pressure at the gauge. If not, the problem is not your sender, it is either the wiring or the gauge itself.

--Geoff

     Do senders like these have two terminals (one for ground) or is the ground done through the fitting threads?

[Geoff]

Both. 

[Oonrahnjay]

Both. 

      So - for the type with two connectors - if you bypass the entire sender and get max reading, it means the circuit up to the gauge and the gauge itself are good.  After that, if you wire a known-good ground to the ground pin, and the reading changes, that points to a fault in the ground path; if not, the problem is likely to be in the sender? 
      My new Cummins engine has two senders; one on-off for the idiot light and one that is resistive for the gauge.  Thanks for this info.