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
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
