Possible Deviation From Specified Value During The Pressure Test (9 Of 11)

Possible Deviation from Specified Value during the Pressure Test
The required cooling output is not attained in the heater and A/C unit evaporator (and in the evaporator for battery cooling). The high pressure increases above specification Low pressure quickly drops to specified value or lower.
Possible causes for the deviation from specified value and their solutions
A/C compressor activation or functionality malfunctioning. Constriction or obstruction in refrigerant circuit Expansion valve malfunctioning -- Check the activation and function of the A/C compressor and service. Use the Vehicle Diagnostic Tester in the"Guided Fault Finding" function of the A/C system and the battery regulation. If not error can be determined run hand over refrigerant circuit to check for differences in temperature. Refer to Refrigerant Circuit .-- If difference in temperature is found at one component: If the hose or pipe is kinked or constricted, replace this component and replace a faulty expansion valve. Refer to Refrigerant Circuit .-- If there is a blockage clean the refrigerant circuit (flush with refrigerant R1234yf). Refer to REFRIGERANT CIRCUIT, CLEANING . Replace the expansion valve for the evaporator in the A/C unit (and for the evaporator for battery cooling) as well as the desiccant bag/dryer cartridge (or receiver/receiver/dryer). Refer to COMPONENTS, REPLACING and Refrigerant Circuit . There is too little refrigerant in the refrigerant circuit. -- Extract refrigerant from the refrigerant circuit. Refer to REFRIGERANT CIRCUIT, DISCHARGING .-- If the extracted refrigerant quantity is significantly less than the specified capacity (more that 100 g (3.5 oz)) and look for leaks and correct. Refer to LEAKS, FINDING . and Technical Data .-- If the extracted refrigerant quantity corresponds to the capacity or is only slightly smaller (maximum 100 g (3.5 oz)) and check the refrigerant shut-off valve for function. Refer to Technical Data and Refrigerant Circuit .
Final Procedures
-- Charge the refrigerant circuit. Refer to REFRIGERANT CIRCUIT, CHARGING .-- Repeat the test. Refer to ELECTRICALLY-DRIVEN A/C COMPRESSOR, CHECKING PRESSURE WITH A/C SYSTEM SWITCHED ON .

NOTE:

If the A/C system function when repeating the test is not OK, replace the expansion valve and desiccant bag/dryer cartridge (or receiver/receiver/dryer) and if equipped refrigerant shut-off valve. Refer to Refrigerant Circuit .

With this malfunction, evaporator may ice up although the quantity of refrigerant in circuit is OK.

If the expansion valve in the heater and A/C unit evaporator or the refrigerant shut-off valve 1 is malfunctioning (permanently closed or does not open sufficiently), the A/C compressor is actuated to maximum output and the low pressure drops to specification or below (compressor draws off refrigerant from low-pressure side). As the refrigerant cannot flow via the expansion valve (the refrigerant shut-off valve), if the cooling output is not attained, high pressure may also not increase or only increase slightly due to the absence of energy. Use the Vehicle Diagnostic Tester in the"Guided Fault Finding" function for the A/C system and the battery regulation. Refer to Refrigerant Circuit .

If the expansion valve on the evaporator for the battery cooling is faulty (or if the functionality or activation of the refrigerant shut-off valve 2 is malfunctioning), constantly closed or does not open enough, then the A/C compressor is likewise activated with the maximum output (the required temperatures in the battery cooling module are not attained). The pressure on the low pressure side only falls to the specified value or lower when there is no cooling output requested at the same time in the heater and A/C unit (the refrigerant shut-off valve 1 is activated and is closed). The A/C compressor extracts the refrigerant from the low pressure side from both evaporators). Since, however, no refrigerant can flow over the expansion valve in the A/C unit (the refrigerant shut-off valve 1) and the cooling output for the battery cooling is not attained (there is a malfunction in the area of the battery cooling), the electrical A/C compressor will be activated with a higher speed. Since, however, no refrigerant can flow through, the pressure on the low pressure side falls below the specified value. In addition, the high pressure may never or only slightly increase, due to the absence of energy. Use the Vehicle Diagnostic Tester in the"Guided Fault Finding" function for the A/C system and the battery regulation. Refer to Refrigerant Circuit .

Since the evaporator output for the battery cooling is noticeably smaller than the evaporator output in the A/C unit, the required specified temperature may still be reached for the battery cooling with too little refrigerant in the circuit, but the specified temperature in the heater and A/C unit evaporator will no longer be attainable (even though the A/C compressor is activated with an increased speed).

If there is too much refrigerant oil in the circuit, the A/C compressor must be emptied and the desiccant bag (the dryer cartridge) or the receiver/receiver/dryer must be replaced. After cleaning (flushing with refrigerant R1234yf) and fill the refrigerant circuit with the correct quantity of refrigerant oil. Refer to REFRIGERANT CIRCUIT, CLEANING , APPROVED REFRIGERANT OILS AND REFRIGERANT OIL CAPACITIES and Refrigerant Circuit .

Refer to Possible Deviation From Specified Value During The Pressure Test (1 Of 11) for further information.