Refrigerant Line Problems The temperature of the airflow from the evaporator has not decreased or has only decreased slightly.
System Condition 1
1. Low-pressure gauge reading is below normal. Refer to Table 1 for normal operating pressure.
2. High-pressure gauge reading is below normal. Refer to Table 1 for normal operating pressure. Note: Ambient temperature is above 21 degrees Celsius (70 degrees Fahrenheit).
3. The temperature of the airflow from the evaporator has only decreased slightly.
Possible Causes A refrigerant line leak can cause insufficient refrigerant in the system.
• Perform a leak test. Refer to the Service Manual, SENR5664, “Testing and Adjusting Refrigerant Leaks – Testing”.
• If a leak is found, recover the refrigerant. Refer to the Service Manual, SENR5664, “Refrigerant Recovery” section.
• Repair all leaks.
• If a significant amount of refrigerant has been lost, be sure to check if the compressor is low on oil.
• Recharge the system with refrigerant. • Evacuate the system. Refer to the Service Manual, SENR5664, “Refrigerant System Testing and Adjustment Section – Evacuation”.
• Add the appropriate amount of refrigerant to the system. Measure the weight of the refrigerant. Refer to the Service Manual, SENR5664, “Refrigerant System Testing and Adjustment Section – Charging”.
• After the system has been charged and operated for at least ten minutes, perform a performance test. Refer to the Service Manual, SENR5664, “Air Conditioning Performance – Testing”. System Condition 2 1. Low-pressure gauge reading is normal. Refer to Table 1 for normal operating pressure.
2. High-pressure gauge reading fluctuates or is unstable.
Possible Causes: Air is present in the system.
• Recover refrigerant from the air conditioning system.
• Evacuate the air conditioning system.
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• Recharge the air conditioning system with refrigerant.
System Condition 3
1. Low-pressure gauge reading is below normal. Refer to Table 1 for normal operating pressure.
2. High-pressure gauge reading is above normal. Refer to Table 1 for normal operating pressure. Note: Ambient temperature is above 21 degrees Celsius (70 degrees Fahrenheit).
3. The airflow temperature from the evaporator is not low enough. Possible Causes: Air or moisture (water) is present in the system.
• Recover the refrigerant. Refer to the service manual, SENR5664, “Refrigerant Recovery” section.
• Replace the receiver drier or inline dryer. The desiccant may have absorbed enough moisture. This will allow water vapor to enter the system.
Refer to Service Manual SENR5664, “Removal and Assembly of Receiver Drier Section – Removal and Installation”. For inline dryers, refer to Service Manual SENR5664, “Removal and Assembly of Inline Refrigerant Dryer Section – Removal and Installation”.
• Evacuate the system. Refer to Service Manual SENR5664, “Testing and Adjusting Refrigerant System Section – Evacuation”.
• Add the appropriate amount of refrigerant to the system. Measure the weight of the refrigerant. Refer to Service Manual SENR5664, “Testing and Adjusting Refrigerant System Section – Charging”.
• After the system has been charged and operated for at least ten minutes, perform a performance test. Refer to Service Manual SENR5664, “Air Conditioning Performance – Testing”. System
Condition 4
1. Low-pressure gauge reading is below normal. 1. For normal operating pressure, please refer to Table 1.
2. The high-pressure gauge reading is normal according to the lower pressure limit range. For normal operating pressure, please refer to Table 1. Note: Ambient temperature is above 21 degrees Celsius (70 degrees Fahrenheit).
3. The airflow temperature from the evaporator is not low enough.
4. Frost has formed on the liquid line or at the top of the receiver-dryer. The liquid line or the top of the receiver-dryer feels very cold to the touch.
Possible Causes:
A blockage in the high-pressure liquid line may cause refrigerant to flow out of the evaporator more quickly. This blockage will result in insufficient refrigerant flowing from the receiver-dryer or inline dryer into the evaporator. A clogged filter or a faulty blower motor can also obstruct airflow.
• Refrigerant Recovery. Please refer to the Service Manual, SENR5664, “Refrigerant Recovery” section.
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• Replace the receiver drier if it is clogged. Refer to the service manual, SENR5664, “Disassembly and Assembly of the Receiver Drier – Removal and Installation”.
• Replace the inline dryer if it is clogged.
• Replace the fluid lines if they are clogged.
• Cover any open lines and connections.
Note: The presence of frost or freezing spots on the lines indicates whether refrigerant flow is obstructed. Additionally, the presence of frost or freezing spots on the receiver drier or inline dryer also indicates whether refrigerant flow is obstructed.
• Replace the filter or clear any blockages.
• Evacuate the system. Refer to the Service Manual, SENR5664, “Refrigerant System Testing and Adjustment Section – Evacuation”.
• Add the appropriate amount of refrigerant to the system. Measure the weight of the refrigerant. Refer to the Service Manual, SENR5664, “Refrigerant System Testing and Adjustment Section – Charging”.
• After the system has been charged and operated for at least ten minutes, perform a performance test. Refer to the Service Manual, SENR5664, “Air Conditioning Performance – Testing”. System Status 5
Note: The system only cools the cab in the morning or evening; it cannot cool the cab during the hottest part of the day.
1. The low-pressure gauge reading is normal, but during testing, the gauge reading may drop to the vacuum range. Refer to Table 1 for normal operating pressure.
2. The high-pressure gauge reading is normal, but when the low-pressure gauge reading drops to the vacuum range, the high-pressure gauge reading will be lower than normal. For normal operating pressure, please refer to Table 1. Note: Ambient temperature is above 21 degrees Celsius (70 degrees Fahrenheit).
3. The airflow from the evaporator is cold, but the airflow temperature will become hot when the low-pressure gauge drops to vacuum.
Possible Causes:
* There is a large amount of moisture in the system.
* The desiccant in the receiver drier or inline dryer has absorbed enough moisture. This moisture will flow out in a high-temperature environment.
* The orifice or expansion valve is frozen, and the ice blocks obstruct the flow of refrigerant.
* Recover refrigerant from the system. Please refer to the Service Manual, SENR5664, “Testing and Adjusting Refrigerant Recovery”.
* Replace the receiver drier or inline dryer. Please refer to the Service Manual, SENR5664, “Removing and Assembling the Receiver Drier – Removal and Installation”. For inline dryers, please refer to the Service Manual, SENR5664, “Removing and Assembling the Inline Refrigerant Dryer – Removal and Installation”.
• Remove moisture from the system. Refer to the Service Manual, SENR5664, “Refrigerant System Testing and Adjustment Section – Evacuation”.
• Add the appropriate amount of refrigerant to the system. Measure the weight of the refrigerant. Refer to the Service Manual, SENR5664, “Refrigerant System Testing and Adjustment Section – Charging”.
• After the system is fully charged and has operated for at least ten minutes, perform a performance test. Refer to the Service Manual, SENR5664, “Air Conditioning Performance – Testing”.
Note: When ice forms in the expansion valve, the low pressure (inlet) will drop to a vacuum. When the low pressure drops to a vacuum, the high pressure (outlet) will also drop.
System Condition 6 1. The low pressure gauge reading remains unchanged. The pressure should rise when the compressor is not operating. Refer to Table 1 for normal operating pressures.
2. The high pressure gauge reading is at the upper limit of the normal range.
Note: Ambient temperature is above 21 degrees Celsius (70 degrees Fahrenheit).
3. The airflow temperature from the evaporator is not low enough.
Possible Causes Air or moisture is present in the system. The system is not fully charged with refrigerant.
• Perform a leak test and carefully inspect the compressor seals. Refer to the Service Manual, SENR 5664, “Refrigerant Leakage Testing and Adjustment Section – Test”.
• Recover refrigerant from the system. Refer to the Service Manual, SENR 5664, “Refrigerant Recovery Testing and Adjustment Section”.
• Repair all leaks.
• Check the compressor for oil shortage.
• Evacuate the system. Please refer to the Service Manual, SENR5664, “Refrigerant System Testing and Adjustment – Evacuation”.
• Add the appropriate amount of refrigerant to the system. Measure the weight of the refrigerant. Please refer to the Service Manual, SENR5664, “Refrigerant System Testing and Adjustment – Charging”.
• After the system has been charged and operated for at least ten minutes, perform a performance test. Please refer to the Service Manual, SENR5664, “Air Conditioning Performance – Testing”.
System Condition 7 1. The low-pressure gauge reading is higher than normal. For normal operating pressure, please refer to Table 1.
2. The high-pressure gauge reading is higher than normal. For normal operating pressure, please refer to Table 1.
Note: Ambient temperature is above 21 degrees Celsius (70 degrees Fahrenheit).
3. The high-pressure (fluid line) is very hot.
4. The compressor is very noisy; the drive belt may be slipping.
Note: The compressor is not operating under extremely high or low temperature conditions. The compressor does not operate under conditions of extremely high humidity.
Possible Causes: The system is overcharged.
• Recover excess refrigerant. Refer to the Service Manual, SENR5664, “Refrigerant Recovery” section.
• Add the appropriate amount of refrigerant to the system. Measure the weight of the refrigerant. Refer to the Service Manual, SENR5664, “Refrigerant System – Charging” section.
• Perform a performance check. Refer to the Service Manual, SENR5664, “Air Conditioning Performance – Testing”.
Note: If the system has not been maintained for a long time, please perform the following procedure. If the system pressure is outside the normal technical parameters,
please also perform the following procedures:
• Refrigerant recovery. Please refer to the Service Manual, SENR5664, “Refrigerant Recovery” section.
• Evacuate the system. Please refer to the Service Manual, SENR5664, “Refrigerant System Testing and Adjustment Section – Evacuation”.
If the system has not been maintained for a long time, replace the receiver drier or inline drier.
• Add the appropriate amount of refrigerant to the system according to its weight. Please refer to the Service Manual, SENR5664, “Refrigerant System Testing and Adjustment Section – Charging”.
• After the system has been charged and operated for at least ten minutes, perform a performance test. Please refer to the Service Manual, SENR5664, “Air Conditioning Performance – Testing”.
System Condition 8
1. The low-pressure gauge reading is higher than normal. For normal operating pressure, please refer to Table 1.
2. The high-pressure gauge reading is lower than normal. For normal operating pressure, please refer to Table 1. Note: If the ambient temperature is above 21 degrees Celsius (70 degrees Fahrenheit), fill the system with refrigerant.
3. The temperature of the airflow from the evaporator is not low enough.
Possible causes:
Internal leak in the compressor.
Leak in the reed valve.
Wear of the compressor piston, seals, or cylinder.
• Check the tension of the compressor drive belt.
• Perform a leak test. Confirm if the problem is with the compressor. Refer to the service manual, SENR5664, “Testing and Adjusting Refrigerant Leaks in the Section – Testing”.
If an internal leak is found, perform the following procedures:
• Replace the compressor. Refer to the service manual, SENR5664, “Removing and Assembling the Refrigeration Compressor in the Section – Removal and Installation”.
• Replace the receiver drier. Refer to the service manual, SENR5664, “Testing and Adjusting the Receiver Drier in the Section – Removal and Installation”.
• Evacuate the system. Please refer to the Service Manual, SENR5664, “Refrigerant System – Evacuation (Test and Adjustment Section)”.
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• Add the appropriate amount of refrigerant to the system according to its weight. Please refer to the Service Manual, SENR5664, “Refrigerant System – Charging (Test and Adjustment Section)”.
• After the system has been charged and operated for at least ten minutes, perform a performance test. 102
