Oil Pressure Test Gauge and VDO gauge question

[montauk]

My oil pressure has been erratic. The sending unit was the original with a date stamp of 9/79 so I replaced it. The gauge still shows the same stuff with the new sending unit. For instance, it will bounce from 2 to 3 bar when it should be around 3 bar (3000 RPM). I hooked up a temporary wire from the new sender to the back of the gauge, same problem. I also disconnected the sending wire to make sure the needle traveled to 5 BAR and back to 0 BAR. I removed all the wires from the back of the gauge and cleaned the connections.

I want to eliminate an actual oil pressure problem from the list of possibilities so I hooked up a Matco mechanical oil gauge. I don't have an adapter for the sending unit fitting so I removed the temperature sender and connected it there. The pressure reading is perfect. It's right at 65 PSI when revved up and idles around 10 PSI. Is this an acceptable connection point for the test gauge? From what I can tell, it's the same oil galley as the pressure sending unit.

Assuming the pressure is good and the wiring is good, there's a chance my new sending unit is bad. Does anyone know the resistance values I should be seeing at various pressures? I really hope that thing isn't bad. It's a pain in the !@#$ to change.

I suppose it could also be the gauge. Any other test for the gauge other than checking to make sure it goes jumps from 0 to 5 BAR by removing the sending wire? If I knew the proper sending unit resistance values, I could hook up a potentiometer and make sure the needle travels smoothly and correctly.

Thanks

Dave