Oil sending unit

Hello all! i have a 2012 Jinma 284 with a Laidong K385 engine and i would like to replace the oil sending unit due to erratic reading on the oil pressure gauge, the gauge included in the dashboard, the needle will move with the throttle and at times will seem to be stuck and then will bounce back and forth a bit and start moving smoothly, it moves anywhere from 4 to 10 on the scale depending on throttle. Now  the sending unit on the tractor has 2 terminal on it but only one wire attached to it, and looking around it does not appear that there is a disconnected wire close by or that there never was, i do not know if the previous owner changed it before, but apparently there is 2 style the old style has only one terminal and the later has 2. The replacement units are not expensive and i want to change it to see if it will fix the problem but with one to buy, any help is appreciated.