Conditions

No/Inefficient Cooling

Fault symptoms
The compressor clutch engages but the system's cooling efficiency is insufficient.

Conditions
The conditions are as follows:
^ Outside temperature>5 °C.
^ Radiator fans are functioning.
^ There is free air flow to the condensers.
^ No difference in temperature between the drier filter inlet and outlet.
^ Pressure at the low-pressure side normally 1.5-2.5 bar.
^ Pressure at the high-pressure side depends on the load on the system.





Diagnostic procedure

1. Checking compressor engagement
^ Start the engine and run it at idling speed.





^ Turn on air recirculation, select maximum heat for both zones and put the fan on maximum speed.





^ Close all the doors and windows. Wait for five minutes.

The compressor should operate continuously.

Is the function correct?
YES
^ Go to step 2.
NO
^ Go to step 9.





2. Checking evaporator temperature in DICE
^ Contact DICE.
^ Read: Evaporator temperature (DICE).
^ The value should be below 10 °C (50 °F).

Is the function correct?
YES
^ Go to step 3.
NO
^ Go to step 6.





3. Checking the function of the shut-off valve
^ Start the engine and run it at idling speed.





^ Select maximum cold for both zones.
^ Check that the temperature of the heat exchanger return line decreases.

Does the temperature decrease?
YES
^ Check the function of the air-mixing flap. Also note that a blocked fresh-air filter can be detrimental to the capacity.
^ Go to step 11.
NO
^ Go to step 4.

4. Checking the vacuum hoses
^ Check the vacuum hoses between the shut-off valve and the intake manifold.

Are the hoses free from defects?
YES
^ Go to step 5.
NO
^ Rectify vacuum hoses.
^ Go to step 11.





5. Checking the power supply.
^ Turn the ignition key to ON.





^ Connect a test lamp between pin 1 on the female connector and a reliable ground.





^ The test lamp should light.

Is the function correct?
YES
^ Go to step 11.
NO
^ Rectify lead in question.
^ Go to step 11.

6. Checking system tightness
^ Check the A/C system for any leaks.

Is the function correct?
YES
^ Go to step 7.
NO
^ Rectify leak and fill the system with correct amount of refrigerant.
^ Go to step 11.

7. Checking the amount of refrigerant
^ Empty the system and check the amount of refrigerant.

Is the system holding the correct amount of refrigerant?
YES
^ Replace: Expansion valve
^ Refill the system with the correct amount of refrigerant.
^ Go to step 8.
NO
^ Refill the system with the correct amount of refrigerant.
^ Go to step 11.

8. Checking evaporator temperature in DICE
^ Read: Evaporator temperature (DICE).
^ The value should be below 10 °C (50 °F).

Is the function correct?
YES
^ Go to step 11.
NO
^ Replace: A/C compressor clutch.
^ Go to step 11.

9. Checking conditions for engagement
^ Check what is disengaging the compressor using the diagnostic tool.
^ Read: Coolant temperature (Trionic).
^ Read: A/C Pressure (DICE).
^ Read: Evaporator temperature (DICE).
^ Select the condition that disengages the compressor.

CONDENSER PRESSURE BELOW 27 BAR
^ Go to step 1O
COOLANT TEMPERATURE ABOVE 125 DEGREES C
^ The A/C malfunction is caused by the coolant temperature being too high. Diagnose the cooling system or Trionic temperature sensor and rectify the fault
^ Go to step 11
EVAPORATOR TEMPERATURE BELOW 0 DEGREES C
^ Replace Temperature sensor, evaporator A/C.
^ Go to step 11

10. Checking the pressure sensor
^ The pressure measured with the pressure gauge on the high-pressure side should correspond to the value for the pressure sensor.

Is the function correct?
YES
^ Empty the system and refill with the correct amount of refrigerant. The probable cause of the high-pressure is too much refrigerant or air in the system.
^ Go to step 11.
NO
^ Replace: Pressure sensor A/C.
^ Go to step 11.





11. Final check
^ Delete diagnostic trouble codes in all systems.
^ Carry out a function check.

Is the function correct?
YES
^ The steps taken to rectify the fault were correct.
NO
^ Before Changing a Control Module