REBUILD KIT- 1W7072 - Caterpillar

Before beginning any test of the electric warning system, check all electrical connections and grounds for good contact.1. Remove the test plug (11) on the accumulator charging valve.2. Install a 0 to 2000 psi (0.0 to 140.6 kg/cm2) gauge in that hole.3. Start the engine. Release the parking brakes. Permit the pressure in the accumulator to go up to cutout pressure.
SCHEMATIC OF ELECTRIC SYSTEM
1. Brake pressure indicator. 2. Ammeter. 3. Warning horn. 4. Terminal. 5. Common terminal. 6. Terminal. 7. Parking brake pressure switch. 8. Inlet manifold pressure switch. 9. Battery. 10. Switch with no moving parts (solid state).4. Stop the engine but do not turn off the disconnect switch.
TEST PLUG LOCATION ON ACCUMULATOR CHARGING VALVE
11. Test plug.5. Look at the test gauge while pushing the brake pedal down several times. Check the test gauge reading at which the ball of the brake pressure indicator (1) turns from green to red. The pressure switch (7) for the parking brake opens and the ball of brake pressure indicator (1) turns at 750 psi (52.7 kg/cm2). If the indicator ball does not turn to red, turn off the disconnect switch. If the indicator ball turns only when the disconnect switch is turned off, install a new brake pressure switch (7). If the indicator ball does not turn when the pressure in the brake circuit is low and the disconnect switch is turned off, install a new brake pressure indicator (1).
PARKING BRAKE PRESSURE SWITCH
7. Switch.Electric Warning Horn
1. Connect a 0 to 100 in. of mercury (0.0 to 2540.0 mm of mercury) Manifold Pressure Gauge or a 0 to 30 psi (0.0 to 2.1 kg/cm2) gauge to an inlet manifold of the engine.2. Pull the parking brake valve handle OUT. This activates the parking brake and stops the flow of any pressure oil to the parking brake and brake pressure switch (7). The electric circuit to the horn is now complete through the brake pressure switch.3. Start the engine. Watch the pressure gauge, put the transmission in third speed forward, push the governor control pedal and check the pressure at which the warning horn makes a sound. The horn makes a sound at 3.06 in. of mercury (77.7 mm of mercury) or 1.5 psi (0.11 kg/cm2) inlet manifold pressure. If it does not, check the components of the warning system using the following procedure:
INLET MANIFOLD PRESSURE SWITCH
8. Switch.4. Stop the engine. Check for a complete circuit in the brake pressure switch (7) from common terminal (5) to terminal (6) to the inlet manifold pressure switch. There must be a complete circuit. If the circuit is not complete install a new switch (7).5. If there is a complete circuit in the brake pressure switch, check the pressure needed to complete the circuit in the inlet manifold pressure switch. If this pressure is not 3.06 in. of mercury (77.7 mm of mercury) or 1.5 psi (0.11 kg/cm2) install a new switch.6. If the problem is still not found, check the horn. Put a