COVER 1552348 - Caterpillar

Illustration 1 g02278663
(1) Passage
(2) Passage
(3) Check ball The shuttle valve sends pressure in order to signal the pump to meet the pressure demand of the hydraulic fan and service brakes. When the service brake pressure is below the cut in pressure, the pressure in passage (2) is greater than the pressure in passage (1). The pressure forces check ball (3) to the left and pressurized oil to exit through passage (1). This signals the pump to upstroke. When the brake system reaches the cut out pressure, the signal pressure for the brake becomes zero. The check ball (3) moves to the right. This movement of the ball allows the pump to sense the requirement for the fan system.