Refrigerant System Charge
STANDARD PROCEDURE - CHARGING A/C SYSTEMPartial Charge
WARNING: REVIEW THE WARNINGS AND CAUTIONS IN THE FRONT BEFORE CHARGING THE REFRIGERANT SYSTEM.
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. 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 Hi.
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 connector from the low pressure cycling clutch switch on the accumulator. Install a jumper wire between the two cavities of the switch 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.
a. 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, the record the temperature of the outlet tube. Subtract the inlet tube temperature reading from the outlet tube temperature reading.
b. If dual probes are used, record the temperatures of both the inlet and outlet tubes. Then substract the inlet tube temperature reading from the outlet tube temperature reading.
Fig.3 Low Charge Determination:
8. See the Low Charge Determination chart to determine the additional charge required. If the measured temperature differential is higher that 22 °C to 26 °C (40 °F to 47 °F), add 0.4kg (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 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 switch connector and plug the connector and plug the connector back into the switch.
Refrigerant Oil Level
When an air conditioning system is assembled at the factory, all components (except the compressor) are refrigerant oil free. After the system has been charged and operated, the oil in the compressor is dispersed through the refrigerant system. The accumulator, evaporator, condenser, and compressor will retain a significant amount of oil.
Fig.4 A/C Service Ports:
Evacuation
Before adding refrigerant, all air must be evacuated from the system.
- Connect a manifold gauge set to the A/C service ports.
- Use a vacuum pump or charging station and evacuate system to 95 kPa (28 inches Hg) for 30 minutes.
- Go to Charging A/C System below.
Charging A/C System
The procedure below should be used to fill the refrigerant charge in the air conditioning system. This A/C system does not have or use a sight glass to check or charge the system.
WARNING:
- REVIEW SAFETY PRECAUTIONS AND WARNINGS BEFORE CHARGING THE REFRIGERANT SYSTEM.
- AVOID BREATHING A/C REFRIGERANT AND LUBRICANT VAPOR OR MIST. EXPOSURE MAY IRRITATE EYES, NOSE AND THROAT. USE ONLY APPROVED SERVICE EQUIPMENT MEETING SAE REQUIREMENTS TO DISCHARGE R-134a SYSTEM. IF ACCIDENTAL SYSTEM DISCHARGE OCCURS, VENTILATE WORK AREA BEFORE RESUMING SERVICE.
- R-134a SERVICE EQUIPMENT OR VEHICLE A/C SYSTEM SHOULD NOT BE PRESSURE TESTED OR LEAK TESTED WITH COMPRESSED AIR. MIXTURE OF AIR and R-134a CAN BE COMBUSTIBLE AT ELEVATED PRESSURES. THESE MIXTURES ARE POTENTIALLY DANGEROUS AND MAY RESULT INFIRE OR EXPLOSION CAUSING INJURY OR PROPERTY DAMAGE.
CAUTION: Do not overcharge refrigerant system, as excessive compressor head pressure can cause noise and system failure.
After the system has been tested for leaks and evacuated, a refrigerant (R-134a) charge can be injected into the system.
NOTE: When connecting the service equipment coupling to the line fitting, verify that the valve of the coupling is fully closed. This will reduce the amount of effort required to make the connection.
1. If using a separate vacuum pump close all valves before disconnecting pump. Connect manifold gauge set to the A/C service ports.
NOTE: The maximum amount of R-134a refrigerant that the air conditioning system holds is 851 grams (1.875 lbs.), 30 oz.
2. Measure refrigerant. Refer to the instructions provided with the equipment being used.
3. Verify engine is shut off. Open the suction and discharge valves. Open the charge valve to allow the refrigerant to flow into the system. When the transfer of refrigerant has stopped, close the suction and discharge valve.
4. If all of the charge did not transfer from the dispensing device, put vehicle controls into the following mode:
- Automatic transaxle in park or manual transaxle in neutral
- Engine idling at 700 rpm
- A/C control set in 100 percent outside air
- Panel mode
- Blower motor ON high speed
- Vehicle windows closed
If the A/C compressor does not engage, test the compressor clutch control circuit and correct any failure.
5. Open the suction valve to allow the remaining refrigerant to transfer to the system.
WARNING: TAKE CARE NOT TO OPEN THE DISCHARGE (HIGH-PRESSURE) VALVE AT THIS TIME.
6. Close all valves and test the A/C system performance.
7. Disconnect the charging station or manifold gauge set. Install the service port caps.