HARNESS AS-PANEL 2353761 - Caterpillar

Illustration 1 g01344052
(1) Brake air relay valve for the service brakes for the front wheels (2) Brake air relay valve for service brakes and for the manual retarder for the rear wheels (3) Double check valveThe brake air relay valves are located on the platform on the right side of the truck near the cab. Brake air relay valve (1) activates the front brake master cylinder when the service brake pedal is applied. The front brake control must be in the ON position. Brake air relay valve (2) activates the rear brake master cylinder when the service brake pedal, or the manual retarder control is applied.When the service brake pedal is pushed with the front brake control in the ON position, signal pressure is sent to the control passage of brake air relay valve (1). This causes an internal valve in brake air relay valve (1) to open. This allows air from the primary air tank to flow through brake air relay valve (1). This air flows to the air chamber of the front brake master cylinder for the front wheels. The front brake master cylinder then engages the brakes for the front wheels.When the service brake pedal is pushed or when the manual retarder is used, signal pressure is sent to the control passage of brake air relay valve (2). This causes an internal valve in brake air relay valve (2) to open. This allows air from the primary air tank to flow through brake air relay valve (2). This air flows to the air chamber of the brake master cylinder for the rear wheels. The rear brake master cylinder then engages the service brakes for the rear wheels.Brake air relay valves (1) and (2) release in the same way. When the brake pedal is released, the signal pressure to the control passage of the brake air relay valve will stop. The internal valve in the brake air relay valve will shift in order to block the flow of air from the primary air tank. When the brake master cylinders do not receive air flow to the air chambers, the brakes are released.Double check valve (3) allows brake air relay valve (1) and the secondary brake inverter valve to share the same air lines to the brake master cylinder for the front wheels.