Possible Deviation From Specified Value During The Pressure Test (6 Of 12)

Possible Deviation from Specified Value during the Pressure Test
High pressure increases above specification The low pressure quickly falls to the target value, The required cooling output is not attained in the front heater and A/C unit evaporator (and/or in the evaporator for cooling the high-voltage components).
Possible causes for the deviation from specified value and their solutions
A/C compressor activation or functionality malfunctioning. If one of the valves installed in the refrigerant circuit is faulty or does not work correctly. Refer to Refrigerant Circuit . Constriction or obstruction in refrigerant circuit Expansion valve malfunctioning -- Check the activation and function of the A/C compressor and service using the Vehicle Diagnostic Tester in the"Guided Fault Finding" function.-- Check the function and activation of the various valves installed in the refrigerant circuit via the pressure distribution in the refrigerant circuit. Use the Vehicle Diagnostic Tester in the"Guided Fault Finding" function. Refer to Refrigerant Circuit .-- Check the refrigerant circuit lines. If the hose or pipe is kinked or constricted, remove this component. Refer to Refrigerant Circuit .-- Run hand over refrigerant circuit to check for differences in temperature (position with a blockage). If there is a blockage clean the refrigerant circuit (flush with refrigerant R1234yf). Refer to REFRIGERANT CIRCUIT, CLEANING .
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:

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 installed shut-off valve 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). Since no (or little) the refrigerant can flow via the expansion valve, 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. Refer to COOLING OUTPUT, CHECKING .

If the expansion valve for the evaporator for cooling the high-voltage components is faulty (or the function and activation is faulty) is always closed or does not open wide enough the A/C compressor is also activated with the maximum output (the required temperatures in the heat exchanger are not reached). The pressure on the low pressure side only then falls to the specified value or lower when at the same time the front heater and A/C unit no cooling output is needed. The A/C compressor extracts the refrigerant from the low pressure side from both evaporators. Because no refrigerant can low over the expansion valve in the front heater and A/C unit and the cooling output in the evaporator for cooling the high voltage battery is not reached (there is a malfunction in the area of the evaporator for the cooling of the high voltage battery) the electric A/C compressor is activated with a higher speed. If not refrigerant can flow the pressure on the low pressure side falls under the specified value, high pressure may also not increase or only increase slightly due to the absence of energy. The same applies if a valve in the refrigerant circuit is not OK a malfunction in the incorporation of the evaporator for cooling the high-voltage battery in the high-voltage system refrigerant circuit or the pump or a valve installed there is not OK. Then the High-Voltage Battery Heat Exchanger is cooled, but the cooled coolant reached the high-voltage battery heat exchanger which should not be cooled. Use the Vehicle Diagnostic Tester in the"Guided Fault Finding" function. Refer to Coolant Circuit .

Refer to Possible Deviation From Specified Value During The Pressure Test (1 Of 12) for additional information.