Those units should be 10-90 ohms if I remember correctly. To test the guage and the wiring going up front, go back to the sending unit and take the wire off, and with the key in run, have someone watch the guage as you ground the sending unit wire, and then take it off ground and let it hang in the air. If the guage goes full scale back and forth when you do this, then it and the wiring are good.