COMPRESSOR GP-REFRIGERANT 3781272 - Caterpillar

Introduction
This information includes the following test and adjust:
Control Manifold (Charging Valve for the Brake Accumulators) "Test Procedure 1" is a quick method for checking the cutout pressure. This procedure also indicates whether the oil pressure switch for the service brakes and the brake oil pressure indicator operate correctly."Test Procedure 2" determines whether the cut-in pressure and the cutout pressure are correct. This procedure also provides the required steps for adjusting the brake accumulator charging valve.Test Preparation
Complete the procedure in the Service Manual module Testing and Adjusting, "Machine Preparation for Troubleshooting" prior to testing the machine.Refer to Testing and Adjusting, "Brake Accumulator - Test and Charge".Refer to Testing and Adjusting, "System Pressure Release".
Illustration 1 g03419816
Steering Frame in the locked position
Move steering frame lock to the LOCKED position.
Stop the engine. Engage the parking brake.
Depress the brake pedal repeatedly until there is no brake oil pressure.Test Procedure 1
Illustration 2 g03419767
Location of panel for access to remote pressure taps
Illustration 3 g03419769
(1) Pressure tap for the brake accumulator charging valveNote: The brake accumulator charging valve is located on the right side of the machine under the operator platform. The remote pressure tap for the valve is located under the access panel that is behind the cab on the left side of the machine.
Connect a 0 to 25,000 kPa (0 to 3,600 psi) pressure gauge at test port (1) .
Observe the pressure gauge. Before you start the engine, the oil pressure must be 0 kPa (0 psi).
Start the engine. Allow the oil pressure to increase to the cutout pressure. The correct cutout pressure should be 14485 345 kPa (2100 50 psi).
After the brake accumulators have been charged and the correct cutout pressure has been obtained, stop the engine.
Turn the engine key start switch to the ON position, but do not start the engine.
Apply the service brakes repeatedly. Pause for a few seconds before each brake application and count the number of applications while you observe the pressure gauge.
Illustration 4 g03419778
Instrument Panel (2) Brake oil pressure indicator.
When the reading on the pressure gauge decreases to 8960 345 kPa (1300 50 psi), brake oil pressure indicator (2) will turn ON. The brake oil pressure switch is located beside accumulator charging valve. The brake accumulator charging valve is located on the right side of the machine under the operator platform.
Continue to apply the service brakes, pausing for a few seconds between each brake application. When the pressure drops off rapidly, this drop in pressure indicates the approximate nitrogen precharge pressure in the brake accumulators.
Determine the number of brake applications that were required before the sudden pressure drop in Step 8. This number should be more than five times.
If the cutout pressure is not within the specification, complete Steps 6 through 11 in "Test Procedure 2". If the nitrogen precharge pressure is not within the specification, see the following reference.ReferenceFor additional information on charging the brake accumulators, refer to the Service Manual for Testing and Adjusting, "Brake Accumulator - Test and Charge".Test Procedure 2
Note: Use the same operational