Look at the foot valve, there usually a 2 wire switch on or near it. If not there, look for a air distribution block for the same type of switch. You will have to check it with a meter or continuity test light. If not on or near the foot valve, it could be a low air alarm switch.
2021 Ram Limited, 3500, Crew Cab, 1075FTPD of Torque!, Max Tow, Long bed, 4 x 4, Dually,
2006 40' Landmark Mt. Rushmore