Partial A/C System Charge
WARNING: OBSERVE ALL REFRIGERANT WARNINGS AND CAUTIONS WHILE RECOVERING REFRIGERANT.REFRIGERANT SYSTEM CHARGE
After the system has been tested for leaks and evacuated, a refrigerant charge can be injected into the system. See Refrigerant Charge Capacity for the proper amount of the refrigerant charge. Charge the system using a recovery/recycling/charging station approved for R-134a refrigerant. This device must meet SAE Standard J2210. Refer to the instructions provided with the equipment for proper operation.
WARNING: OBSERVE ALL REFRIGERANT WARNINGS AND CAUTIONS WHILE RECOVERING REFRIGERANT.
PARTIAL CHARGE METHOD
The partial charge method is used to add a partial charge to a system that is low on refrigerant. To perform this procedure the evaporator inlet and outlet tube temperatures are measured. The temperature difference is measured with a temperature meter with one or two clamp-on thermocouple probes. The difference between the evaporator inlet and outlet tube temperatures will determine the amount of refrigerant needed.
Before adding a partial charge, check for refrigerant system leaks. See Refrigerant System Leaks in this group for the procedures. If a leak is found, make the necessary repairs before attempting a full or partial refrigerant system charge.
1. Attach a manifold gauge set to the service ports.
2. Attach the two clamp-on thermocouple probes to the inlet and outlet tubes of the evaporator coil.
a. If a single thermocouple probe is used, attach the probe to the evaporator inlet tube just before the collar of the refrigerant line connector fitting. The probe must make contact with the bottom surface of the inlet tube.
b. If dual thermocouple probes are used, attach probe 1 to the evaporator inlet tube, and probe 2 to the evaporator outlet tube. Attach both probes to the tubes just before the collar of the refrigerant line connector fittings. The probes must make contact with the bottom surfaces of the inlet and outlet tubes.
3. Open all of the windows or doors of the passenger compartment. Set the air conditioning controls to A/C, Panel, Recirc (temperature control knob in the full cool position) and the blower motor switch on High.
4. Start the engine and hold the engine idle speed at 1,000 rpm. Allow the engine to warm up to normal operating temperature.
5. The compressor clutch may cycle, depending upon ambient temperature, humidity, and the refrigerant system charge level. If the compressor clutch cycles, unplug the wire harness connector from the low pressure cycling clutch switch on the accumulator. Install a jumper wire between the two cavities of the switch wire harness connector.
6. Hold the engine idle speed at 1,000 rpm.
7. Allow three to five minutes for the refrigerant system to stabilize, then record the temperatures of the evaporator inlet and outlet tubes.
c. If a single probe is used, record the temperature of the inlet tube. Then remove the probe from the inlet tube and attach it to the outlet tube just before the collar of the refrigerant line connector fitting. The probe must make contact with the bottom surface of the tube. Allow the thermocouple and meter time to stabilize, then record the temperature of the outlet tube. Subtract the inlet tube temperature reading from the outlet tube temperature reading.
d. If dual probes are used, record the temperatures of both the inlet and outlet tubes. Then subtract the inlet tube temperature reading from the outlet tube temperature reading.
8. See the Low Charge Determination chart to determine the additional charge required. If the measured temperature differential is higher than 22 °C-26 °C (40 °F-47 °F), add 0.4 kg (14 oz.) of refrigerant.
9. Allow three to five minutes for the refrigerant system to stabilize, then take a second set of thermocouple measurements. Record the temperature difference and see the Low Charge Determination chart to determine if an additional charge is required.
10. Record the compressor discharge pressure. If the reading is higher than the pressure shown in the Compressor Discharge Pressure chart, the system could be overcharged. If the reading is equal to, or lower, than the pressure shown in the chart, continue with this procedure.
11. EXAMPLE: The ambient temperature is 21 °C (70 °F). The evaporator inlet tube temperature is 12 °C (54 °F) and the evaporator outlet tube temperature is 10 °C (50 °F). Subtract the inlet tube temperature from the outlet tube temperature. The difference is -2 °C (-4 °F). With a -2 °C (-4 °F) temperature differential at 21 °C (70 °F) ambient temperature, the system is fully charged.
12. Add enough refrigerant to bring the refrigerant system up to a full charge.
13. Remove the jumper wire from the low pressure cycling clutch switch wire harness connector and plug the connector back into the switch.