Need Info on Series I Oil Pressure Gauge

[djwarner]

I ran into a local gauge manufacturer who actually sells a 10 Bar oil pressure sender. I asked if his sender would work with our Series I 0-140 psig gauges and he replied that he know without more information about our gauges. ( 1 bar is 14.7 psig)

What is unique about his sender is that it is not a dual purpose sender like almost all of the other senders available for our cars. Dual purpose senders are intended for use with idiot lights and go open when oil pressure goes below approximately 10 psig. This is what causes our gauges to go to zero while idling after pulling off the interstate. His sender does not have this feature.

For those who do not know, Series I cars came with a 0-140 psig gauge that was changed to 0-90 psig after the first year of production. Datsun discontinued supplying  10 Bar senders but continued selling them until existing stocks were exhausted. Later they came out with a service bulletin instructing to replace the gauge with a 0-90 psig unit to match the later sender. Many Series I cars never had the gauges replaced and are a mismatch for the available senders. The  0-140 psig are sought after by restorers seeking originality for Series I cars.

The 6 Bar senders commonly available will work with our 0-140 psig gauges, but with unknown calibration. And of course they all have the idiot light function.

After my engine overhaul, I began to suspect that the two gauges (0-90 and 0-140) might have the identical movements and the only difference is the marking on the dial face. But I have no way of verifying this. 

I have been looking for specs for our gauges to no avail. Basically, I need to know what resistance at the sender corresponds to 0, middle marker (70 psig), and 140 psig our gauges. 

Any information on the two gauges would be helpful.