Here is an instruction show you guide how to check and test refrigerant pressure switch for Kubota U48-4 and U55-4 excavator.
Preparations:
2022 Kubota Takeuchi Diagmaster v22.08.01 v4.1.2 Software Free Download
Kubota DST-i Diagnostic Adapter
Kubota EPC Spare Parts Catalogue 2021.06 Download
Procedures:
When a pressure switch (inside the high-pressure/low-pressure switch) is operating normally, electricity is conducted (ON) and when an abnormal pressure occurs, it trips the switch, blocking the electricity (OFF).
Manifold gauge connections
1 Close the HI (high-pressure side) valve (3) and the LO (low-pressure side) valve (2) of the manifold gauge (1) securely.
2 Connect the red charging hose (4) to the HI (high-pressure side) charge valve (1) and the blue charging hose (5) to the LO (low-pressure side) charge valve (2).
3 Open the manifold gauge’s HI (high-pressure side) valve (3) a little and press on the valve core to expel any air inside its charging hose (4). Then close the HI (high-pressure side) valve (3) tightly.
4 Open the manifold gauge’s LO (low-pressure side) valve (2) a little and press on the valve core to expel any air inside its charging hose (5). Then close the LO (low-pressure side) valve (2) tightly.
(1) Manifold gauge
(2) Low-pressure valve
(3) High-pressure valve
(4) Red charging hose
(5) Blue charging hose
When refrigerant pressure is rising (OFF)
1Start the engine and set it at 1,500 rpms. Turn the AC switch on the control panel on, set the fan switch to HI and set the temperature control lever to the max cool position.
2 Cover the front of the condenser with cardboard or the like and raise the pressure on the high pressure side of the AC cycle.
3 Once the pressure on the high-pressure side rises, the high-pressure switch operates, turning the magnetic clutch of the compressor off. When it does so, read the HI (high-pressure) gauge of the manifold gauge and if it reads higher than the pressure setting, replace the pressure switch
(8).
• Pressure setting on the high-pressure side of the switch:
Switches off at approximately 3.14 MPa (32 kgf/cm2, 460 psi) or higher
When refrigerant pressure is dropping (OFF)
1Remove the connector of the pressure switch (8).
2Measure the resistance between the terminals of the pressure switch with a circuit tester. It should register 0Ω unless there is insufficient gas due to a leak or unless the pressure switch is faulty.
• Pressure setting on the low-pressure side of the switch:
Switches off at approximately 0.196 MPa (2.0 kgf/cm2, 28 psi)
More repair case for Kubota,please refer to:Kubota Trouble Repair