Refrigerant Circuit Problems
System Condition 9
1. Low pressure gauge reading is above normal. For normal operating pressures, refer to Table 1.
2. High pressure gauge reading is normal or low. For normal operating pressures, refer to Table 1.
Note: Ambient temperature is above 21°C (70°F) and the system has a refrigerant charge that is full.
3. The temperature of the air flow from the evaporator is warm.
4. The suction hose and the evaporator is covered with moisture (sweating).
Probable Cause
Flow of refrigerant through the evaporator coil is excessive. The expansion valve could be stuck or held in the OPEN position.
1. Test the expansion valve for the correct operation. Use the following procedure.
* Position the air conditioner temperature control knob in the maximum COOL position and the fan switch in the HIGH position.
* Cool the head of the expansion valve diaphragm chamber and the capillary tube with ice or liquid nitrogen. Record the low pressure gauge reading. The low pressure gauge should indicate a vacuum.
* If the low pressure gauge indicates a vacuum, place a hand over the expansion valve diaphragm chamber. The hand will warm the expansion valve diaphragm chamber. In order to ensure the correct operation of the expansion valve, cool the head of the expansion valve diaphragm chamber and the capillary tube with ice or liquid nitrogen again. If the operation of the expansion is correct, refer to Step 2.
* If the low pressure gauge does not indicate the proper operation of the expansion valve, recover the refrigerant from the system. Refer to the Service Manual, SENR5664, "Refrigerant Recovery" section in Testing and Adjusting.
* Replace the expansion valve. Refer to the Service Manual, SENR5664, "Expansion Valve - (Air Conditioner) Remove and Install" section in Disassembly and Assembly.
Note: The sensing bulb must be installed correctly in order to ensure the proper operation of the expansion valve.
* 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.
2. If the pressure gauge indicates the correct operation of the expansion valve, perform the following procedure.
* Use a 8P-6355 Clip in order to hold the sensing bulb onto the evaporator outlet pipe. The sensing bulb should be as close to the evaporator as possible. The bulb should be upstream of the pressure sensing connection on the evaporator outlet pipe. The following items must be wound tightly with 5P-7070 Strip Insulation : the clip, the sensing bulb and the outlet pipe. There should be no insulation between the bulb and the outlet pipe.
* In order to ensure that the system operates correctly, perform a performance check. Refer to "Performance Checks for the Air Conditioning System" section.
Illustration can look at above
Expansion valve in the open position (Typical Example)
(1) Capillary tube
(2) Expansion valve diaphragm chamber
(3) Inlet
(4) Outlet
System Condition 9
1. Low pressure gauge reading is above normal. For normal operating pressures, refer to Table 1.
2. High pressure gauge reading is normal or low. For normal operating pressures, refer to Table 1.
Note: Ambient temperature is above 21°C (70°F) and the system has a refrigerant charge that is full.
3. The temperature of the air flow from the evaporator is warm.
4. The suction hose and the evaporator is covered with moisture (sweating).
Probable Cause
Flow of refrigerant through the evaporator coil is excessive. The expansion valve could be stuck or held in the OPEN position.
1. Test the expansion valve for the correct operation. Use the following procedure.
* Position the air conditioner temperature control knob in the maximum COOL position and the fan switch in the HIGH position.
* Cool the head of the expansion valve diaphragm chamber and the capillary tube with ice or liquid nitrogen. Record the low pressure gauge reading. The low pressure gauge should indicate a vacuum.
* If the low pressure gauge indicates a vacuum, place a hand over the expansion valve diaphragm chamber. The hand will warm the expansion valve diaphragm chamber. In order to ensure the correct operation of the expansion valve, cool the head of the expansion valve diaphragm chamber and the capillary tube with ice or liquid nitrogen again. If the operation of the expansion is correct, refer to Step 2.
* If the low pressure gauge does not indicate the proper operation of the expansion valve, recover the refrigerant from the system. Refer to the Service Manual, SENR5664, "Refrigerant Recovery" section in Testing and Adjusting.
* Replace the expansion valve. Refer to the Service Manual, SENR5664, "Expansion Valve - (Air Conditioner) Remove and Install" section in Disassembly and Assembly.
Note: The sensing bulb must be installed correctly in order to ensure the proper operation of the expansion valve.
* 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.
2. If the pressure gauge indicates the correct operation of the expansion valve, perform the following procedure.
* Use a 8P-6355 Clip in order to hold the sensing bulb onto the evaporator outlet pipe. The sensing bulb should be as close to the evaporator as possible. The bulb should be upstream of the pressure sensing connection on the evaporator outlet pipe. The following items must be wound tightly with 5P-7070 Strip Insulation : the clip, the sensing bulb and the outlet pipe. There should be no insulation between the bulb and the outlet pipe.
* In order to ensure that the system operates correctly, perform a performance check. Refer to "Performance Checks for the Air Conditioning System" section.
Illustration can look at above
Expansion valve in the open position (Typical Example)
(1) Capillary tube
(2) Expansion valve diaphragm chamber
(3) Inlet
(4) Outlet
