Differential Warning Switch: Notes

Switch is used to warn vehicle operator that one of the hydraulic systems has failed. When hydraulic pressure is equal in both front and rear systems, switch piston remains centered and does not contact terminal in switch cylinder bore. Switch includes a centering spring on each side of piston to hold piston in centered position. If pressure falls in one of the systems, hydraulic pressure moves piston towards inoperative side. Shoulder of piston then contacts switch terminal to provide a ground for warning lamp circuit and light warning lamp.