RETAINER 4T4521 - Caterpillar

Troubleshooting the System with the Manifold Gauge Set
Illustration 1 g00862735
Control Panel Type 1
Illustration 2 g03342362
Control Panel Type 2
(1) Power switch
(2) Automatic temperature control switch
(3) Air conditioning override switch
(4) Temperature select switches
(5) Preset temperature display
(6) Fan speed switches
(7) Air outlet select switch
(8) Air inlet select switch
(9) Control panel
(10) Switch for defroster The following conditions must exist in order to perform the checking procedures: Engine ... Normal operating temperatureDoor ... OpenAir inlet select switch (8) ... RecirculationTemperature of air at inlet ... 30° to 35°C (86° to 95°F)Fan speed switch (6) ... HIEngine rpm ... 1500 rpmTemperature select switch (4) ... MAX COOLThe following readings are correct under normal operating conditions.
Illustration 3 g00475933 (L) Low-pressure side 0.15 to 0.25 MPa (22 to 36 psi) (H) High-pressure side 1.37 to 1.57 MPa (200 to 230 psi) ProblemThe system has an insufficient amount of refrigerant charge.Symptoms
Pressure is low on the low side and the high side.
Bubbles continuously appear in the sight glass.
The cooling effect is poor.Cause A refrigerant leak exists. This leak causes the amount of refrigerant charge to be low.Corrective Measures
Isolate the leak and repair the refrigerant leak.
Recharge the air conditioning system. Refer to the Testing and Adjusting, "Refrigerant System - Charge" section for the proper procedure. ProblemThe system is overcharged with refrigerant, which causes poor cooling by the condenser.Symptoms
Pressure is high on the low side and the high side.
Bubbles do not appear in the sight glass even when the system is operated slowly.
The cooling effect is poor.Cause The system is overcharged with refrigerant and the condenser is not cooling well.Corrective Measures
Recover the refrigerant until the level is correct. Refer to the Specifications, "System Capacities for Refrigerant" section for the proper amount of charge.
Clean the condenser.
Check the engine cooling fan. ProblemMoisture is present in the refrigerant circuit.Symptom
After a few minutes of use, the low-pressure side gradually indicates negative pressure.CauseMoisture has entered the refrigerant circuit.Corrective Measures
Replace the receiver-dryer. Refer to the Operation and Maintenance Manual, "Refrigerant Receiver-Dryer - Replace" section for the proper procedure.
Evacuate the system. Refer to the Testing and Adjusting, "Refrigerant System - Evacuate" section for the proper procedure.
Charge the system. Refer to the Testing and Adjusting, "Refrigerant System - Charge" section for the proper procedure. ProblemThe compressor is supplying insufficient compression.Symptoms
The manifold gauge set shows excessive high pressure on the low side.
The high-pressure side measures pressure that is too low.
Pressure equalizes when the compressor is turned OFF.CauseThe compressor is failing.Corrective MeasureCheck and repair the compressor.ProblemThe refrigerant does not circulate properly.Symptoms
Negative pressure is indicated immediately on the low side when the system is completely clogged.
Negative pressure is indicated gradually on the low side when the system is sometimes clogged.
Air temperature is different before clogging and after clogging.Cause Debris collects around the small holes of the expansion valve. Another possibility is that moisture is freezing around the expansion valve.Corrective Measures
Replace the receiver-dryer. Refer to the Operation and Maintenance Manual, "Refrigerant Receiver-Dryer - Replace" section for the proper procedure.
Evacuate the system. Refer to the Testing and Adjusting, "Refrigerant System - Evacuate" section for the proper