ADAPTER 4789270 - Caterpillar

Illustration 1 g00763484
View from the Right Rear of the Tractor (1) Tractor relay valve
Illustration 2 g00763485
View Under the Rear of the Scraper (2) Scraper relay valveRelay valve (1) for the tractor is located at the rear of the tractor above the transmission. Relay valve (2) for the scraper is located above the scraper air reservoir. Each relay valve controls the flow of air from the air reservoirs to the brakes.
Illustration 3 g00727089
Relay Valve (3) Diaphragm assembly (4) Control passage (5) Valve passage (6) Delivery passage (7) Valve (8) Supply passage (9) Valve (10) Spring (11) Exhaust passageSupply passage (8) is connected to the air reservoirs. Spring (10) holds valve (7) seated in order to stop the flow of air to delivery passage (6) .When air pressure is sent to control passage (4), diaphragm assembly (3) will be forced down. As diaphragm assembly (3) moves down, valve (10) makes contact with valve (7). This closes the exhaust passage inside valve (7). Diaphragm assembly (3) will push valve (7) downward. This will open a passage so that air from supply passage (8) will go through the valve and out delivery passage (6) to the brake actuators.When the air pressure to control passage (4) is released, spring (10) will push valve (7) upward. This will stop the flow of air pressure through supply passage (8). Air pressure in delivery passage (6) will push diaphragm assembly (3) upward against the cover of the valve. Valve (10) will move away from valve (7), which will open a passage through valve (7). Thus, the air pressure can go out through exhaust passage (11).