Some background on this so-called "Gauge"; da Sender is just a switch and the gauge indicated whether there is OIL PSI or not.
From the 1996 F-150, F-250, F-350, Bronco, F-Super Duty Motorhome Chassis Workshop Manual:
Oil Pressure Gauge
The oil pressure gauge is a magnetic movement design consisting of a bobbin/coil assembly, a return to zero magnet and a primary magnet. The shaft and pointer are connected to the primary magnet. The bobbin/coil assembly is pressed into a metal housing which has two holes for dial mounting.
The gauge operates through a pressure activated switch
. When the engine is started engine oil pressure closes the switch, providing a ground circuit for the gauge coil. Current flow through the gauge coil to ground causes the primary magnet and pointer to rotate, providing an oil pressure reading on the dial face.
The oil pressure gauge does not require adjustment, calibration or maintenance. Also, never remove the pointer indicator from its shaft.
Oil Pressure Switch
The oil pressure switch controls the magnetic oil pressure gauge's pointer position. The oil pressure switch closes under normal engine operating conditions (oil pressure above 42 kPa [6 lb/sq in]). The oil pressure switch opens with the engine (6007) off and no oil pressure.
Oil Pressure Sender
Check gauge operation as follows
With the key in RUN and the engine off, disconnect wiring connector at the switch. The gauge should indicate on the LOW graduation or below.
Connect the wiring connector to the engine block ground. The gauge should indicate just slightly above mid-scale.
If the oil pressure gauge tests within calibration, replace oil pressure switch.
If the gauge still tests out of calibration, replace oil pressure gauge.
Oil Pressure Mod to Actual PSI "...short R in PCB..." info & NAPA Sender, etc.
Source: by Steve83 (Steve, That dirty old truck) at http://www.supermotors.net/vehicles/...y/media/281470
Oil Pressure Mod to Actual PSI "...short R in PCB..."; "...So someone told me that my 92-96 F-series Oil Pressure gauge really isn't a gauge, it's more of and idiot indicator, this bothered me...:mad: So I decided to test the theory and of course they were right, wether it has 20#'s of pressure or 60#'s of pressure it stays in the exact same spot on the gauge. I tested the sending unit and it is a ON/OFF to ground switch. So I remembered that my old Fox body Mustang had a real working gauge so I found one of those big bulky sending units and the extension and installed it instead. Then it read really low on the gauge while idling.:headscratch: I looked at the EVTM and saw that there is a 20 Ohm resistor inline on the circuit. I pulled the cluster and sure enough there is a resistor smack dab on the cluster paper behind the oil psi gauge. I removed it and the gauge went dead. I soldered a jumper piece inline and POOF. See the pictures and video below..."
Source: by drvovru at http://fullsizebronco.com/forum/showthread.php?t=183293
Installation, Oil Pressure, Water Temp & Transmission Temp., Auto Meter Night Vision in a 95
Source: by Ian L (stangmata, stangmata50l, Bronco) at Stang's Gauge install
MORE INFO LINKs in my site @ http://www.broncolinks.com/index.php?index=949
other gauge info incl Instrument Cluster Removal @ http://www.broncolinks.com/index.php?index=429