Welcome to iRV2.
Sorry you're here with problems.
I don't know if Spartan ever used the same type of gauge system that gave Freightliner air gauge operation problems ; VDC ( Vehicle Data Center ) that they used for a few years; 98 > 02.
Could you provide some more info on your coach .
Chassis year ?
Have you checked the back of the gauge to see if there is an air line attached , or just wiring ?
Have you tried calling , Spartan Motor Home Support, with your serial number ?
They should be able to provide you with an air system diagram, that would narrow down locations of sensors.
1-800-543-4277