How to check step by step Refrigerant Circuit Problems part 2

Refrigerant Circuit Problems

System Condition 4

1. Low pressure gauge reading is below normal. For normal operating pressures, refer to Table 1.

2. High pressure gauge reading is normal to the below normal range. For normal operating pressures, refer to Table 1.

Note: Ambient temperature is above 21°C (70°F).

3. The temperature of the air flow from the evaporator is partially cool.

4. The high side liquid line or the receiver-dryer is frosted. The high side liquid line or the receiver-dryer is cool to the touch.

Probable Cause

Restriction in the high pressure liquid line can cause the refrigerant to be removed from the evaporator at a faster rate. The restriction can cause the evaporator to be low on refrigerant from the receiver-dryer or from the in-line dryer. Clogged filters or a failure of the blower motor can cause possible restrictions to the air flow.

* Recover the refrigerant. Refer to the Service Manual, SENR5664, "Refrigerant Recovery" section.

* If the restriction is found at the receiver-dryer, replace the receiver-dryer. Refer to the Service Manual, SENR5664, "Receiver-Dryer - Remove and Install" section in Disassembly and Assembly.

* If the restriction is found at the in-line dryer, replace the in-line dryer.

* If the restriction is found at the liquid line, replace the liquid line.

* Cap all the open lines and fittings.

Note: Restrictions of the refrigerant flow are identified by frost or cold spots in the line. Also, restrictions of the refrigerant flow are identified by frost or cold spots in the receiver-dryer or the in-line dryer.

* Replace filters or remove any of the restrictions.

* Evacuate the system. Refer to the Service Manual, SENR5664, "Refrigerant System - Evacuate" section in Testing and Adjusting.

* Charge the system with the correct amount of refrigerant. Measure the refrigerant by weight. Refer to the Service Manual, SENR5664, "Refrigerant System - Charge" section in Testing and Adjusting.

* After the system is charged and operated for a minimum of ten minutes, perform a performance check. Refer to "Performance Checks for the Air Conditioning System" section.

System Condition 5

Note: The system only cools the cab in the morning and in the evening. The system does not cool the cab during the hot part of the day.

1. Low pressure gauge reading is normal, but the gauge reading may drop into the vacuum range during the testing procedure. For normal operating pressures, refer to Table 1.

2. The high pressure gauge reading is normal, but the gauge reading is below normal when the low pressure gauge drops into the vacuum range. For normal operating pressures, refer to Table 1.

Note: Ambient temperature is above 21°C (70°F).

3. Air flow from the evaporator is very cold, but the air flow will become warm when the low pressure gauge drops into vacuum.

Probable Cause

The system has a large amount of moisture. The desiccant in the receiver-dryer or the in-line dryer is full of water. The water is released during high ambient temperatures. Ice collects in the orifice or the expansion valve and the ice can block the flow of refrigerant.

* Recover the refrigerant from the system. Refer to the Service Manual, SENR5664, "Refrigerant Recovery" section in Testing and Adjusting.

* Replace the receiver-dryer or the in-line dryer. Refer to the Service Manual, SENR5664, "Receiver-Dryer - Remove and Install" section in Disassembly and Assembly. For in-line dryers, refer to the Service Manual, SENR5664, "In-Line Refrigerant Dryer - Remove and Install" section in Disassembly and Assembly.

* Remove the moisture from the system. Refer to the Service Manual, SENR5664, "Refrigerant System - Evacuate" section in Testing and Adjusting.

* Charge the system with the correct amount of refrigerant. Measure the refrigerant by weight. Refer to the Service Manual, SENR5664, "Refrigerant System - Charge" section in Testing and Adjusting.

* After the system is charged and operated for a minimum of ten minutes, perform a performance check. Refer to "Performance Checks for the Air Conditioning System" section.

Note: Low pressure (suction) drops into vacuum when ice forms in the expansion valve. High pressure (discharge) drops when low pressure drops into vacuum.

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How to Check step by step Refrigerant Circuit Problems part 1

Refrigerant Circuit Problems

There is no or only little cool temperature to the air flow from the evaporator.

System Condition 1

1. Low pressure gauge reading is below normal. For normal operating pressures, refer to Table 1.

2. High pressure gauge reading is below normal. For normal operating pressures, refer to Table 1.

Note: Ambient temperature is above 21°C (70°F).

3. From the evaporator, the temperature of the air flow is partially cool.

Probable Cause

Leaks in the refrigerant circuit will cause the system to be low on refrigerant.

* Perform a leak test. refer to the Service Manual, SENR5664, "Refrigerant Leakage - Test" section in Testing and Adjusting.

* If leaks are found, recover the refrigerant. Refer to the Service Manual, SENR5664, "Refrigerant Recovery" section.

* Repair leaks.

* If a large amount of refrigerant was lost, it is important to check the compressor for loss of oil.

* Perform a partial charge of the system.

* Evacuate the system. Refer to the Service Manual, SENR5664, "Refrigerant System - Evacuate" section in Testing and Adjusting.

* Charge the system with the correct amount of refrigerant. Measure the refrigerant by weight. Refer to the Service Manual, SENR5664, "Refrigerant System - Charge" section in testing and adjusting.

* After the system is charged and operated for a minimum of ten minutes, perform a performance check. Refer to "Performance Checks for the Air Conditioning System" section.

System Condition 2

1. Low pressure gauge reading is normal. For normal operating pressures, refer to Table 1.

2. High pressure gauge reading bounces or the reading is unsteady.

Probable Cause

Air is in the system.

* Reclaim the refrigerant from the air conditioning system.

* Evacuate the air conditioning system.

* Recharge the air conditioning system.

System Condition 3

1. Low pressure gauge reading is below normal. For normal operating pressures, refer to Table 1.

2. High pressure gauge reading is above normal. For normal operating pressures, refer to Table 1.

Note: Ambient temperature is above 21°C (70°F).

3. The temperature of the air flow from the evaporator is warm.

Probable Cause

Air or moisture (water) in the system

* Recover the refrigerant. Refer to the Service Manual, SENR5664, "Refrigerant Recovery" section.

* Replace the receiver-dryer or the in-line dryer. The desiccant may be full of moisture. This will release water into the system. Refer to the Service Manual, SENR5664, "Receiver-Dryer - Remove and Install" section in Disassembly and Assembly. For in-line dryers, refer to the Service Manual, SENR5664, "In-Line Refrigerant Dryer - Remove and Install" section in Disassembly and Assembly.

* Evacuate the system. Refer to the Service Manual, SENR5664, "Refrigerant System - Evacuate" section in Testing and Adjusting.

* Charge the system with the correct amount of refrigerant. Measure the refrigerant by weight. Refer to the Service Manual, SENR5664, "Refrigerant System - Charge" section in Testing and Adjusting.

* After the system is charged and operated for a minimum of ten minutes, perform a performance check. Refer to "Performance Checks for the Air Conditioning System" section.

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Due Air Conditioning System Troubleshooting

Heating and Air Conditioning System Troubleshooting

Refrigerant Quick-Check Procedure for R-134a Expansion Valve And Orifice Tube Systems

Note: This procedure does not call for the installation of the manifold gauge set. The procedure should be used only as an indication of the actual system condition. For the detailed troubleshooting procedures, refer to the "Problem Solving Procedure" section.

Note: In order to use this procedure, the temperature of the ambient air must be at least 21°C (70°F).

1. Start the engine and run the engine at approximately 1000 rpm. Move the control knob on the air conditioner to the position of MAXIMUM so that cooling is at a maximum. In order to stabilize the system, put the fan switch in the HIGH position and operate the system for a minimum of 10 minutes.

For systems that have air conditioner quick disconnects, the dryer can be removed without recovering the refrigerant.

* Replace the receiver-dryer. Refer to the Service Manual, SENR5664, "Receiver-Dryer - Remove and Install" section in Disassembly and Assembly.

* Perform a leak test. Refer to the Service Manual, SENR5664, "Refrigerant Leakage - Test" section in Testing and Adjusting.

* Perform a performance check. Refer to "Performance Checks for the Air Conditioning System" section.

2. Check for restrictions that are present in the refrigerant lines from the compressor to the receiver-dryer. The refrigerant lines and the components that are high pressure and high temperature come from the outlet side of the compressor. The lines go to the inlet side of the expansion valve or orifice tube. The outlet side will be warm during normal operation. Heavy frost or a decrease in the temperature in a line or in a component on the high pressure side may be an indication of a restriction or blockage.

1. If there is no evidence of a restriction in the condenser coil, the receiver-dryer or refrigerant lines from the compressor to the receiver-dryer, use the procedure in Step 3.

2. If there is a restriction in the condenser coil, the receiver-dryer or refrigerant lines from the compressor to the receiver-dryer, perform the following procedures.

* Recover the refrigerant. Refer to the Service Manual, SENR5664, "Refrigerant Recovery" section.

* Remove the restriction or replace the component.

* Evacuate the system. Refer to the Service Manual, SENR5664, "Refrigerant System - Evacuate" section in Testing and Adjusting.

* Charge the system with the correct amount of refrigerant. Measure the refrigerant by weight. Refer to the Service Manual, SENR5664, "Refrigerant System - Charge" section in Testing and Adjusting.

* Perform a leak test. Refer to the Service Manual, SENR5664, "Refrigerant Leakage - Test"section in Testing and Adjusting.

* Perform a performance check. Refer to "Performance Checks for the Air Conditioning System" section.

3. If frost is present on the expansion valve, check the moisture indicator on the receiver-dryer. If the indicator is pink or white, and the receiver does not have air conditioner quick disconnects, perform the following procedures.

* Recover the refrigerant. Refer to the Service Manual, SENR5664, "Refrigerant Recovery" section.

* Replace the receiver-dryer. Refer to the Service Manual, SENR5664, "Receiver-Dryer - Remove and Install" section in Disassembly and Assembly.

* Evacuate the system. Refer to the Service Manual, SENR5664, "Refrigerant System - Evacuate" section in Testing and Adjusting.

* Charge the system with the correct amount of refrigerant. Measure the refrigerant by weight. Refer to the Service Manual, SENR5664, "Refrigerant System - Charge" section in Testing and Adjusting.

* Perform a leak test. Refer to the Service Manual, SENR5664, "Refrigerant Leakage - Test" section in Testing and Adjusting.

* Perform a performance check. Refer to "Performance Checks for the Air Conditioning System" section.

Refer to the Service Manual, SENR5664, "Receiver-Dryer - Remove and Install" section if the receiver-dryer has air conditioner quick disconnects. Refer to the Service Manual, SENR5664, "In-Line refrigerant Dryer - Remove and Install" section if the in-line dryer has air conditioner quick disconnects.

4. On air conditioning systems that have a dryer with a moisture indicator, if the indicator is blue and the system is free of moisture, the expansion valve may be blocked.

* Recover the refrigerant. Refer to the Service Manual, SENR5664, "Refrigerant Recovery" section.

* Replace the expansion valve. Refer to the Service Manual, SENR5664, "Expansion Valve - (Air Conditioner) Remove and Install" section in Disassembly and Assembly.

* Evacuate the system. Refer to the Service Manual, SENR5664, "Refrigerant System - Evacuate" section in Testing and Adjusting.

* Charge the system with the correct amount of refrigerant. Measure the refrigerant by weight. Refer to the Service Manual, SENR5664, "Refrigerant System - Charge" section in Testing and Adjusting.

* Perform a leak test. Refer to the Service Manual, SENR5664, "Refrigerant Leakage - Test"section in Testing and Adjusting.

* Perform a performance check. Refer to "Performance Checks for the Air Conditioning System" section.

3. Low system charge is indicated. Perform a leak test.

Note: If the system is very low on refrigerant, a partial charge may be needed before you perform a leak test.

* Recover the remaining refrigerant. Refer to the Service Manual, SENR5664, "Refrigerant Recovery" section.

* Repair all leaks.

* Evacuate the system. Refer to the Service Manual, SENR5664, "Refrigerant System - Evacuate" section in Testing and Adjusting.

* Charge the system with the correct amount of refrigerant. Measure the refrigerant by weight. Refer to the Service Manual, SENR5664, "Refrigerant System - Charge" section in Testing and Adjusting.

* Perform a performance check. Refer to "Performance Checks for the Air Conditioning System" section.

4. Feel the low pressure line and feel the high pressure line at the compressor. In order to indicate normal systems operation, the high pressure line to the condenser coil must be warm, while the low pressure line to the evaporator coil must be cool.

* The high pressure line and the low pressure line at the compressor have a minimal temperature difference between the two lines. Use the procedure in Step 5.

* If there is a definite temperature difference between the high pressure line and the low pressure line at the compressor, the system is operating correctly. The high pressure line will be warm. The low pressure line will be cool. Use the procedure in Step 6.

5.If the system has no refrigerant charge or if the system is nearly empty of refrigerant charge, perform the following procedure:

* Stop the engine.

* Perform a partial charge of the system.

* Perform a leak test. Refer to the Service Manual, SENR5664, "Refrigerant Leakage - Test" section in Testing and Adjusting.

* Repair leaks.

* Evacuate the system. Refer to the Service Manual, SENR5664, "Refrigerant System - Evacuate" section in Testing and Adjusting.

* Charge the system with the correct amount of refrigerant. Measure the refrigerant by weight. Refer to the Service Manual, SENR5664, "Refrigerant System - Charge" section in Testing and Adjusting.

* Perform a performance check. Refer to "Performance Checks for the Air Conditioning System" section.

6. An overcharge of the system is possible even though the system can have a definite difference in temperature at the low pressure line and at the high pressure line.

* Recover the refrigerant. Refer to the Service Manual, SENR5664, "Refrigerant Recovery" section.

* Evacuate the system. Refer to the Service Manual, SENR5664, "Refrigerant System - Evacuate" section in Testing and Adjusting.

* Charge the system with the correct amount of refrigerant. Measure the refrigerant by weight. Refer to the Service Manual, SENR5664, "Refrigerant System - Charge" section in Testing and Adjusting.

* Perform a performance check. Refer to the "Performance Checks for the Air Conditioning System" section.

Note: For an orifice tube system, an additional inspection is required. The additional inspection procedure determines the level of the system charge. When both the inlet of the accumulator and the outlet of the accumulator are cool to the touch, the system is charged correctly.

If the outlet is warmer than the inlet, the system may not contain enough refrigerant.

* Recover the refrigerant. Refer to the Service Manual, SENR5664, "Refrigerant Recovery" section.

* Evacuate the system. Refer to the Service Manual, SENR5664, "Refrigerant System - Evacuate" section in Testing and Adjusting.

* Charge the system with the correct amount of refrigerant. Measure the refrigerant by weight. Refer to the Service Manual, SENR5664, "Refrigerant System - Charge" section in testing and adjusting.

* Perform a leak test. Refer to the Service Manual, SENR5664, "Refrigerant Leakage - Test" section in Testing and Adjusting.

* Perform a performance check. Refer to "Performance Checks for the Air Conditioning System" section.

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Due Inspection Air Conditioning System

Performance Checks for the Air Conditioning System

A performance check of the air conditioning system must be made with a manifold gauge set. The manifold gauge set must be connected to the service ports on the compressor.

Note: Before you conduct a performance check, refer to the Service Manual, SENR5664, "Visual Inspection" section.

Refer to the Service Manual, SENR5664, "Machine Preparation for Troubleshooting" section before service work is performed on the air conditioning system.

1. Install the manifold gauge set. Refer to the Service manual, SENR5664, "Manifold Gauge Set (Refrigerant) - Install" section.

2. Start the engine and operate the engine at 1000 rpm. Move the temperature control knob to the maximum cool position. Put the fan switch in the HIGH position on the AIR CONDITIONING side. In order to stabilize the system, operate the system for a minimum of ten minutes. Operate the engine at 1000 rpm.

During normal operation of the air conditioning system in 21°C (70°F) weather, the discharge pressure will be 820 to 1300 kPa (120 to 190 psi). The pressure will be 70 to 130 kPa (10 to 20 psi). Refer to Table 1 for temperature range. The outside temperature and humidity will have an effect on the pressures. If the outside temperature is high, the discharge pressure will be high.

In very hot weather, the suction and the discharge pressures will be high. In cooler weather, the suction and the discharge pressure will be normal or the pressure can be lower.

If the suction and the discharge pressures are not within the normal operating range, refer to the "Problem Solving" section.

Note: Most system failures are caused by improper refrigerant charge. Refrigerant charge should be measured by weight only. Do not use gauge pressure when you charge the system with refrigerant.

Problem Solving

The following problem solving section is provided for identifying and correcting problems that may occur in the air conditioning system. Several problems can have the same system condition or similar system conditions. Before you start the procedure in order to correct the problems, it is necessary to be complete in the diagnosis of the problems.

The problem solving procedures are based on the system condition during the problem. In order to indicate the system pressures, the manifold gauge set must be installed. The manifold gauge set is used only in order to diagnose problems. The refrigerant lines can give an indication of system operation that is abnormal. Temperature differences between the high pressure side and the low pressure side can be an indication of abnormal operation in a line. This can also be found by cold spots (frost) on the line. In R134a air conditioning systems, the lines can have spots of frost and the system can be operating normally. Frost will most often form after the orifice and on the lower portion of the accumulator. The temperature of the air flow from the evaporator will also indicate a problem with the system. Knowing the complete system condition is an important step in making a correct diagnosis.

Note: R134a air conditioning system problem diagnosis requires a combination of symptoms or indicators in order to correctly identify problems and solve problems.

Problem Solving Procedure

1. Install the manifold gauge set. Refer to the Service Manual, SENR5664, "Manifold Gauge Set (Refrigerant) - Install" section in Testing and Adjusting.

2. Run the engine at 1000 rpm. Put the air conditioner temperature control knob in the Maximum COOL position. Put the fan switch in the HIGH position on the AIR CONDITIONING side. In order to stabilize the system, operate the engine for a minimum of ten minutes.

3. Adjust the engine speed to approximately 1300 to 1400 rpm. Record the readings on the low pressure gauges and the high pressure gauges. The gauge readings will be a partial indication of the system condition.

Note: When the ambient temperature is above 21°C (70°F), a low pressure gauge reading of 70 to 138 kPa (10 to 20 psi) is a normal operating pressure for the air conditioning system. Also, when the ambient temperature is above 21°C (70°F), a high pressure gauge reading of 820 to 1300 kPa (120 to 190 psi) is a normal operating pressure for the air conditioning system. In very hot weather, the low pressure readings and the high pressure readings will be at the high end of the normal operating range. In cooler weather, the low pressure reading will be in the middle to the low end of the normal operating range, while the high pressure reading will be low. For the correct gauge reading in relation to ambient temperature condition, refer to Table 1.

Note: All pressures are given as a guide only. Weight is the only absolute means of determining proper refrigerant charge. Improper refrigerant charge will cause premature failure of the compressor

Table. Pressure Range

Ambient Air Temperature : C° (F°)
High Pressure Test Fitting : kPa (psi) (2)
Low Pressure Test Fitting : kPa (psi) (3)

Ambient Air Temperature : 21°C (70°F)
High Pressure Test Fitting : 820 to 1300 kPa (120 to 190 psi)
Low Pressure Test Fitting : 70 to 138 kPa (10 to 20 psi)

Ambient Air Temperature : 27°C (80°F)
High Pressure Test Fitting : 950 to 1450 kPa (140 to 210 psi)
Low Pressure Test Fitting : 70 to 173 kPa (10 to 25 psi)

Ambient Air Temperature : 32°C (90°F)
High Pressure Test Fitting : 1175 to 1650 kPa (170 to 240 psi)
Low Pressure Test Fitting : 105 to 210 kPa (15 to 30 psi)

Ambient Air Temperature : 38°C (100°F)
High Pressure Test Fitting : 1300 to 1850 kPa (190 to 270 psi)
Low Pressure Test Fitting : 105 to 210 kPa (15 to 30 psi)

Ambient Air Temperature : 43°C (110°F)
High Pressure Test Fitting : 1450 to 2075 kPa (210 to 300 psi)
Low Pressure Test Fitting : 105 to 210 kPa (15 to 30 psi)

( 1 ) This table is only for reference.
( 2 ) Pressure may be slightly higher in very humid conditions and lower in very dry conditions.
( 3 ) Pressure before clutch disengagement

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How to Adjust Thermostat

Systems Operation
Air Conditioning and Heating R-134a for All Caterpillar Products

Heating and Air Conditioning Control System

Adjustable Thermostat
An adjustable thermostat contains two temperature control knobs. The temperature control knob for the air conditioning system is connected to an adjustable thermostat. A thermostat is a switch. Changes in the temperature will open the thermostat. Changes in the temperature will also close the thermostat. When the temperature control knob is in the OFF position, the electric circuit that connects the adjustable thermostat and the magnetic clutch is OPEN. In the OFF position, the compressor does not operate. The temperature of the air and the position of the temperature control knob determines if the switch is CLOSED. When the switch is CLOSED, current moves through the thermostat to the coil assembly in the magnetic clutch and the compressor operates. The temperature of the air through the evaporator coil is monitored by a capillary tube that is placed between the fins of the evaporator coil.

The temperature control knob for heating is connected to the heater control valve. The temperature of the cab is maintained by the position of the air conditioning and heating temperature control knobs.

Nonadjustable Thermostat (Freeze Control System)

Illustration picture at above
A nonadjustable thermostat contains one temperature control knob. The temperature control knob is connected to the heater control valve, which controls the flow of coolant through the heater coil. The temperature of the air across the evaporator coil is preset by the nonadjustable thermostat. The temperature of the cab is maintained by the position of the temperature control knob on the heater.

Condensation that is frozen will restrict the air flow through the evaporator coils. The compressor will continue operating only if the condensation does not freeze. In order to prevent the condensation from freezing, the thermostat switch opens at a temperature of approximately -1.1°C (30°F). Also, the thermostat switch closes at approximately 2.2°C (36°F). When the switch opens, the electric circuit that connects the switch to the magnetic clutch is OPEN and the compressor does not operate. When the switch is CLOSED, the current moves through the switch to the coil assembly in the magnetic clutch and the compressor operates.

In order to operate the system in the correct manner, the heater core supply must not be closed. Also, in order to operate the system in the correct manner, the return coolant line valve must not be closed.

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