System Charge Level Test

WARNING: REFER TO THE WARNINGS AND CAUTIONS FOR THIS SYSTEM BEFORE PERFORMING THE FOLLOWING OPERATION. FAILURE TO FOLLOW THE WARNINGS AND CAUTIONS COULD RESULT IN POSSIBLE PERSONAL INJURY OR DEATH.

NOTE: Always refer to the underhood HVAC Specification Label for the refrigerant fill capacity of the vehicle being serviced.

The procedure that follows should be used to determine whether the refrigerant system contains the proper refrigerant charge. Symptoms of an improper refrigerant charge (low) include: poor air conditioner performance, fog emitted from the air conditioner outlets, a hissing sound from the expansion valve/evaporator area. There are two different methods with which the refrigerant charge level may be tested:

Charge Determination Chart (Ambient Test Condition 85 Deg F):

1. Using a DRBIII(R) scan tool, a thermocouple and the Charge Determination Chart.
2. Using a manifold gauge set, a thermocouple and the Charge Determination Chart.

A temperature probe is required to measure liquid line temperature. The clamp-on, Type K thermocouple temperature probe used in this procedure is available through the DaimlerChrysler Professional Service Equipment (PSE) program. This probe (PSE #66-324-0014 or #80PK-1A) is compatible with temperature-measuring instruments that accept Type K thermocouples, and have a miniature connector input. Other temperature probes are available through aftermarket sources; however, all references in this procedure will reflect the use of the probe made available through the PSE program.

In order to use the temperature probe, a digital thermometer will also be required. If a digital thermometer is not available, an adapter is available through the PSE program that will convert any standard digital multimeter into a digital thermometer. This adapter is designed to accept any standard Type K thermocouple. If a digital multimeter is not available, this tool is also available through the PSE program.

NOTE: When connecting the service equipment couplings to the refrigerant system service ports, be certain that the valve of each coupling is fully closed. This will reduce the amount of effort required to make the connection.

1. Remove the caps from the refrigerant system service ports and attach a manifold gauge set or a R-134a refrigerant recovery/recycling/charging station that meets SAE Standard J2210 to the refrigerant system.
2. Attach a clamp-on thermocouple to the liquid line. The thermocouple must be placed as close to the A/C pressure transducer as possible to accurately observe liquid line temperature.
3. Bring the refrigerant system up to operating temperature and pressure. This is done by allowing the engine to run at idle under the following conditions for five minutes.
a. Front windows are open.
b. Transaxle in Park.
c. Front heater-A/C controls set to outside air, full cool, panel mode, blower high, and compressor engaged.
d. If the vehicle is so equipped, the rear heater-A/C controls must be set to full cool and blower

4. Raise the liquid line (discharge) pressure to about 1793 kPa (260 psi) by placing a piece of cardboard over part of the front side of the condenser. To place the cardboard properly, remove the upper radiator sight shield from the front fascia. Cover only enough of the condenser to raise and maintain the liquid line pressure at the specified level.
5. Observe the liquid line (discharge) pressure and liquid line temperature. Using the Charge Determination Chart, determine whether the refrigerant system is operating within the Proper Charge Range.
a. If the refrigerant system is operating in the Undercharged area of the chart, add 0.057 kilogram (0.125 pound or 2 ounces) of refrigerant to the system.
b. If the refrigerant system is operating in the Overcharged area of the chart, reclaim 0.057 kilogram (0.125 pound or 2 ounces) of refrigerant from the system.
6. Recheck the system charge level following each refrigerant adjustment. Continue this process until the system readings are in the Proper Charge Range area on the Charge Determination Chart.